Precalculus 2e

# Chapter 3

### 3.1Complex Numbers

1.

$−24 =0+2i 6 −24 =0+2i 6$

2. 3.

$(3−4i)−(2+5i)=1−9i (3−4i)−(2+5i)=1−9i$

4.

$−8−24i −8−24i$

5.

$18+i 18+i$

6.

$102−29i 102−29i$

7.

$− 3 17 + 5i 17 − 3 17 + 5i 17$

1.

The path passes through the origin and has vertex at $( −4,7 ), ( −4,7 ),$ so $(h)x=– 7 16 (x+4) 2 +7. (h)x=– 7 16 (x+4) 2 +7.$ To make the shot, $h( −7.5 ) h( −7.5 )$ would need to be about 4 but $h(–7.5)≈1.64; h(–7.5)≈1.64;$ he doesn’t make it.

2.

$g(x)= x 2 −6x+13 g(x)= x 2 −6x+13$ in general form; $g(x)= (x−3) 2 +4 g(x)= (x−3) 2 +4$ in standard form

3.

The domain is all real numbers. The range is $f(x)≥ 8 11 , f(x)≥ 8 11 ,$ or $[ 8 11 ,∞ ). [ 8 11 ,∞ ).$

4.

y-intercept at (0, 13), No $x- x-$ intercepts

5.
1. 3 seconds
2. 256 feet
3. 7 seconds

### 3.3Power Functions and Polynomial Functions

1.

$f(x) f(x)$ is a power function because it can be written as $f(x)=8 x 5 . f(x)=8 x 5 .$ The other functions are not power functions.

2.

As $x x$ approaches positive or negative infinity, $f( x ) f( x )$ decreases without bound: as $x→±∞ x→±∞$, $f(x)→−∞ f(x)→−∞$ because of the negative coefficient.

3.

The degree is 6. The leading term is $− x 6 . − x 6 .$ The leading coefficient is $−1. −1.$

4.

As $x→∞,f(x)→−∞;asx→−∞,f(x)→−∞. x→∞,f(x)→−∞;asx→−∞,f(x)→−∞.$ It has the shape of an even degree power function with a negative coefficient.

5.

The leading term is $0.2 x 3 , 0.2 x 3 ,$ so it is a degree 3 polynomial. As $x x$ approaches positive infinity, $f( x ) f( x )$ increases without bound; as $x x$ approaches negative infinity, $f( x ) f( x )$ decreases without bound.

6.

y-intercept $(0,0); (0,0);$ x-intercepts $(0,0),(–2,0), (0,0),(–2,0),$ and $(5,0) (5,0)$

7.

There are at most 12 $x- x-$ intercepts and at most 11 turning points.

8.

The end behavior indicates an odd-degree polynomial function; there are 3 $x- x-$ intercepts and 2 turning points, so the degree is odd and at least 3. Because of the end behavior, we know that the lead coefficient must be negative.

9.

The $x- x-$ intercepts are $(2,0),(−1,0), (2,0),(−1,0),$ and $(5,0), (5,0),$ the y-intercept is $(0,2), (0,2),$ and the graph has at most 2 turning points.

### 3.4Graphs of Polynomial Functions

1.

y-intercept $(0,0); (0,0);$ x-intercepts $(0,0),(–5,0),(2,0), (0,0),(–5,0),(2,0),$ and $(3,0) (3,0)$

2.

The graph has a zero of –5 with multiplicity 3, a zero of –1 with multiplicity 2, and a zero of 3 with multiplicity 2.

3. 4.

Because $f f$ is a polynomial function and since $f(1) f(1)$ is negative and $f(2) f(2)$ is positive, there is at least one real zero between $x=1 x=1$ and $x=2. x=2.$

5.

$f(x)=− 1 8 (x−2) 3 (x+1) 2 (x−4) f(x)=− 1 8 (x−2) 3 (x+1) 2 (x−4)$

6.

The minimum occurs at approximately the point $(0,−6.5), (0,−6.5),$ and the maximum occurs at approximately the point $(3.5,7). (3.5,7).$

### 3.5Dividing Polynomials

1.

$4 x 2 −8x+15− 78 4x+5 4 x 2 −8x+15− 78 4x+5$

2.

$3 x 3 −3 x 2 +21x−150+ 1,090 x+7 3 x 3 −3 x 2 +21x−150+ 1,090 x+7$

3.

$3 x 2 −4x+1 3 x 2 −4x+1$

### 3.6Zeros of Polynomial Functions

1.

$f(−3)=−412 f(−3)=−412$

2.

The zeros are 2, –2, and –4.

3.

There are no rational zeros.

4.

The zeros are

5.

$f(x)=− 1 2 x 3 + 5 2 x 2 −2x+10 f(x)=− 1 2 x 3 + 5 2 x 2 −2x+10$

6.

There must be 4, 2, or 0 positive real roots and 0 negative real roots. The graph shows that there are 2 positive real zeros and 0 negative real zeros.

7.

3 meters by 4 meters by 7 meters

### 3.7Rational Functions

1.

End behavior: as $x→±∞,f(x)→0; x→±∞,f(x)→0;$ Local behavior: as $x→0,f(x)→∞ x→0,f(x)→∞$ (there are no x- or y-intercepts)

2. The function and the asymptotes are shifted 3 units right and 4 units down. As $x→3,f(x)→∞, x→3,f(x)→∞,$ and as $x→±∞,f(x)→−4. x→±∞,f(x)→−4.$

The function is $f(x)= 1 (x−3) 2 −4. f(x)= 1 (x−3) 2 −4.$

3.

$12 11 12 11$

4.

The domain is all real numbers except $x=1 x=1$ and $x=5. x=5.$

5.

Removable discontinuity at $x=5. x=5.$ Vertical asymptotes: $x=0,x=1. x=0,x=1.$

6.

Vertical asymptotes at $x=2 x=2$ and $x=–3; x=–3;$ horizontal asymptote at $y=4. y=4.$

7.

For the transformed reciprocal squared function, we find the rational form. $f(x)= 1 (x−3) 2 −4= 1−4 (x−3) 2 (x−3) 2 = 1−4( x 2 −6x+9) (x−3)(x−3) = −4 x 2 +24x−35 x 2 −6x+9 f(x)= 1 (x−3) 2 −4= 1−4 (x−3) 2 (x−3) 2 = 1−4( x 2 −6x+9) (x−3)(x−3) = −4 x 2 +24x−35 x 2 −6x+9$

Because the numerator is the same degree as the denominator we know that as $x→±∞,f(x)→−4;soy=–4 x→±∞,f(x)→−4;soy=–4$ is the horizontal asymptote. Next, we set the denominator equal to zero, and find that the vertical asymptote is $x=3, x=3,$ because as $x→3,f(x)→∞. x→3,f(x)→∞.$ We then set the numerator equal to 0 and find the x-intercepts are at $(2.5,0) (2.5,0)$ and $(3.5,0). (3.5,0).$ Finally, we evaluate the function at 0 and find the y-intercept to be at $( 0, −35 9 ). ( 0, −35 9 ).$

8.

Horizontal asymptote at $y= 1 2 . y= 1 2 .$ Vertical asymptotes at $x=1andx=3. x=1andx=3.$ y-intercept at $( 0, 4 3 . ) ( 0, 4 3 . )$

x-intercepts at $(–2,0) (–2,0)$ is a zero with multiplicity 2, and the graph bounces off the x-axis at this point. $(2,0) (2,0)$ is a single zero and the graph crosses the axis at this point. 1.

$f −1 ( f( x ) )= f −1 ( x+5 3 )=3( x+5 3 )−5=( x−5 )+5=x f −1 ( f( x ) )= f −1 ( x+5 3 )=3( x+5 3 )−5=( x−5 )+5=x$ and $f( f −1 ( x ) )=f( 3x−5 )= ( 3x−5 )+5 3 = 3x 3 =x f( f −1 ( x ) )=f( 3x−5 )= ( 3x−5 )+5 3 = 3x 3 =x$

2.

$f −1 (x)= x 3 −4 f −1 (x)= x 3 −4$

3.

$f −1 (x)= x−1 f −1 (x)= x−1$

4.

$f −1 (x)= x 2 −3 2 ,x≥0 f −1 (x)= x 2 −3 2 ,x≥0$

5.

$f −1 (x)= 2x+3 x−1 f −1 (x)= 2x+3 x−1$

### 3.9Modeling Using Variation

1.

$128 3 128 3$

2.

$9 2 9 2$

3.

$x=20 x=20$

### 3.1 Section Exercises

1.

Add the real parts together and the imaginary parts together.

3.

$i i$ times $i i$ equals –1, which is not imaginary. (answers vary)

5.

$−8+2i −8+2i$

7.

$14+7i 14+7i$

9.

$− 23 29 + 15 29 i − 23 29 + 15 29 i$

11.

2 real and 0 nonreal

13. 15. 17.

$8−i 8−i$

19.

$−11+4i −11+4i$

21.

$2−5i 2−5i$

23.

$6+15i 6+15i$

25.

$−16+32i −16+32i$

27.

$−4−7i −4−7i$

29.

25

31.

$2− 2 3 i 2− 2 3 i$

33.

$4−6i 4−6i$

35.

$2 5 + 11 5 i 2 5 + 11 5 i$

37.

$15i 15i$

39.

$1+i 3 1+i 3$

41.

$1 1$

43.

$−1 −1$

45.

128i

47.

$( 3 2 + 1 2 i ) 6 =−1 ( 3 2 + 1 2 i ) 6 =−1$

49.

$3i 3i$

51.

0

53.

5 – 5i

55.

$−2i −2i$

57.

$9 2 − 9 2 i 9 2 − 9 2 i$

### 3.2 Section Exercises

1.

When written in that form, the vertex can be easily identified.

3.

If $a=0 a=0$ then the function becomes a linear function.

5.

If possible, we can use factoring. Otherwise, we can use the quadratic formula.

7.

$g(x)= (x+1) 2 −4, g(x)= (x+1) 2 −4,$ Vertex $( −1,−4 ) ( −1,−4 )$

9.

$f(x)= ( x+ 5 2 ) 2 − 33 4 , f(x)= ( x+ 5 2 ) 2 − 33 4 ,$ Vertex $( − 5 2 ,− 33 4 ) ( − 5 2 ,− 33 4 )$

11.

$f(x)=3 (x−1) 2 −12, f(x)=3 (x−1) 2 −12,$ Vertex $(1,−12) (1,−12)$

13.

$f(x)=3 ( x− 5 6 ) 2 − 37 12 , f(x)=3 ( x− 5 6 ) 2 − 37 12 ,$ Vertex $( 5 6 ,− 37 12 ) ( 5 6 ,− 37 12 )$

15.

Minimum is $− 17 2 − 17 2$ and occurs at $5 2 . 5 2 .$ Axis of symmetry is $x= 5 2 . x= 5 2 .$

17.

Minimum is $− 17 16 − 17 16$ and occurs at $− 1 8 . − 1 8 .$ Axis of symmetry is $x=− 1 8 . x=− 1 8 .$

19.

Minimum is $− 7 2 − 7 2$ and occurs at $−3. −3.$ Axis of symmetry is $x=−3. x=−3.$

21.

Domain is $( −∞,∞ ). ( −∞,∞ ).$ Range is $[2,∞). [2,∞).$

23.

Domain is $( −∞,∞ ). ( −∞,∞ ).$ Range is $[−5,∞). [−5,∞).$

25.

Domain is $( −∞,∞ ). ( −∞,∞ ).$ Range is $[−12,∞). [−12,∞).$

27.

${ 2i 2 ,−2i 2 } { 2i 2 ,−2i 2 }$

29.

${ 3i 3 ,−3i 3 } { 3i 3 ,−3i 3 }$

31.

${2+i,2−i} {2+i,2−i}$

33.

${2+3i,2−3i} {2+3i,2−3i}$

35.

${5+i,5−i} {5+i,5−i}$

37.

${2+2 6 ,2−2 6 } {2+2 6 ,2−2 6 }$

39.

${ − 1 2 + 3 2 i,− 1 2 − 3 2 i } { − 1 2 + 3 2 i,− 1 2 − 3 2 i }$

41.

${ − 3 5 + 1 5 i,− 3 5 − 1 5 i } { − 3 5 + 1 5 i,− 3 5 − 1 5 i }$

43.

${ − 1 2 + 1 2 i 7 ,− 1 2 − 1 2 i 7 } { − 1 2 + 1 2 i 7 ,− 1 2 − 1 2 i 7 }$

45.

$f(x)= x 2 −4x+4 f(x)= x 2 −4x+4$

47.

$f(x)= x 2 +1 f(x)= x 2 +1$

49.

$f(x)= 6 49 x 2 + 60 49 x+ 297 49 f(x)= 6 49 x 2 + 60 49 x+ 297 49$

51.

$f(x)=− x 2 +1 f(x)=− x 2 +1$

53. Vertex $( 1,−1 ), ( 1,−1 ),$ Axis of symmetry is $x=1. x=1.$ Intercepts are $(0,0),(2,0). (0,0),(2,0).$

55. Vertex $( 5 2 , −49 4 ), ( 5 2 , −49 4 ),$ Axis of symmetry is $x= 5 2 , x= 5 2 ,$ intercepts: $(6,0), (−1,0). (6,0), (−1,0).$

57. Vertex $( 5 4 ,− 39 8 ), ( 5 4 ,− 39 8 ),$ Axis of symmetry is $x= 5 4 . x= 5 4 .$ Intercepts are $( 0,−8 ). ( 0,−8 ).$

59.

$f(x)= x 2 −4x+1 f(x)= x 2 −4x+1$

61.

$f(x)=−2 x 2 +8x−1 f(x)=−2 x 2 +8x−1$

63.

$f(x)= 1 2 x 2 −3x+ 7 2 f(x)= 1 2 x 2 −3x+ 7 2$

65.

$f(x)= x 2 +1 f(x)= x 2 +1$

67.

$f(x)=2− x 2 f(x)=2− x 2$

69.

$f(x)=2 x 2 f(x)=2 x 2$

71.

The graph is shifted up or down (a vertical shift).

73.

50 feet

75.

Domain is $(−∞,∞). (−∞,∞).$ Range is $[−2,∞). [−2,∞).$

77.

Domain is $(−∞,∞) (−∞,∞)$ Range is $(−∞,11]. (−∞,11].$

79.

$f(x)=2 x 2 −1 f(x)=2 x 2 −1$

81.

$f(x)=3 x 2 −9 f(x)=3 x 2 −9$

83.

$f(x)=5 x 2 −77 f(x)=5 x 2 −77$

85.

50 feet by 50 feet. Maximize $f(x)=− x 2 +100x. f(x)=− x 2 +100x.$

87.

125 feet by 62.5 feet. Maximize $f(x)=−2 x 2 +250x. f(x)=−2 x 2 +250x.$

89.

$6 6$ and $−6; −6;$ product is –36; maximize $f(x)= x 2 +12x. f(x)= x 2 +12x.$

91.

2909.56 meters

93.

\$10.70

### 3.3 Section Exercises

1.

The coefficient of the power function is the real number that is multiplied by the variable raised to a power. The degree is the highest power appearing in the function.

3.

As $x x$ decreases without bound, so does $f( x ). f( x ).$ As $x x$ increases without bound, so does $f( x ). f( x ).$

5.

The polynomial function is of even degree and leading coefficient is negative.

7.

$f(x)f(x)$ is a power function because it contains a variable base raised to a fixed power. It is also a polynomial, with all coefficients except one equal to zero.

9.

Neither

11.

Neither

13.

Degree = 2, Coefficient = –2

15.

Degree =4, Coefficient = –2

17.

As $x→∞ x→∞$, $f(x)→∞f(x)→∞$, as $x→−∞x→−∞$, $f(x)→∞ f(x)→∞$

19.

As $x→−∞ x→−∞$, $f(x)→−∞f(x)→−∞$, as $x→∞x→∞$, $f(x)→−∞ f(x)→−∞$

21.

As $x→−∞ x→−∞$, $f(x)→−∞f(x)→−∞$,as $x→∞x→∞$, $f(x)→−∞ f(x)→−∞$

23.

As $x→∞x→∞$, $f(x)→∞f(x)→∞$, as $x→−∞x→−∞$,$f(x)→−∞ f(x)→−∞$

25.

y-intercept is $(0,12), (0,12),$ t-intercepts are

27.

y-intercept is $(0,−16). (0,−16).$ x-intercepts are $(2,0) (2,0)$ and $(−2,0). (−2,0).$

29.

y-intercept is $(0,0). (0,0).$ x-intercepts are $(0,0),(4,0), (0,0),(4,0),$ and $( −2,0 ). ( −2,0 ).$

31.

3

33.

5

35.

3

37.

5

39.

Yes. Number of turning points is 2. Least possible degree is 3.

41.

Yes. Number of turning points is 1. Least possible degree is 2.

43.

Yes. Number of turning points is 0. Least possible degree is 1.

44.

No.

45.

Yes. Number of turning points is 0. Least possible degree is 1.

47.
$x x$ $f( x ) f( x )$
10 9,500
100 99,950,000
–10 9,500
–100 99,950,000

as $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→∞ f(x)→∞$

49.
$x x$ $f( x ) f( x )$
10 –504
100 –941,094
–10 1,716
–100 1,061,106

as $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→−∞ f(x)→−∞$

51. The $y- y-$ intercept is $( 0,0 ). ( 0,0 ).$ The $x- x-$ intercepts are $( 0,0 ),( 2,0 ). ( 0,0 ),( 2,0 ).$As $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→∞ f(x)→∞$

53. The $y- y-$ intercept is $( 0,0 ) ( 0,0 )$ . The $x- x-$ intercepts are $( 0,0 ),( 5,0 ),( 7,0 ). ( 0,0 ),( 5,0 ),( 7,0 ).$ As $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→∞ f(x)→∞$

55. The $y- y-$ intercept is $( 0,0 ). ( 0,0 ).$ The $x- x-$ intercept is $( −4,0 ),( 0,0 ),( 4,0 ). ( −4,0 ),( 0,0 ),( 4,0 ).$ As $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→∞ f(x)→∞$

57. The $y- y-$ intercept is $( 0,−81 ). ( 0,−81 ).$ The $x- x-$ intercept are $( 3,0 ),( −3,0 ). ( 3,0 ),( −3,0 ).$ As $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→∞ f(x)→∞$

59. The $y- y-$ intercept is $( 0,0 ). ( 0,0 ).$ The $x- x-$ intercepts are $( −3,0 ),( 0,0 ),( 5,0 ). ( −3,0 ),( 0,0 ),( 5,0 ).$ As $x→−∞ x→−∞$, $f(x)→∞f(x)→∞$, as $x→∞x→∞$, $f(x)→∞ f(x)→∞$

61.

$f(x)= x 2 −4 f(x)= x 2 −4$

63.

$f(x)= x 3 −4 x 2 +4x f(x)= x 3 −4 x 2 +4x$

65.

$f(x)= x 4 +1 f(x)= x 4 +1$

67.

$V(m)=8 m 3 +36 m 2 +54m+27 V(m)=8 m 3 +36 m 2 +54m+27$

69.

$V(x)=4 x 3 −32 x 2 +64x V(x)=4 x 3 −32 x 2 +64x$

### 3.4 Section Exercises

1.

The $x- x-$ intercept is where the graph of the function crosses the $x- x-$ axis, and the zero of the function is the input value for which $f(x)=0. f(x)=0.$

3.

If we evaluate the function at $a a$ and at $b b$ and the sign of the function value changes, then we know a zero exists between $a a$ and $b. b.$

5.

There will be a factor raised to an even power.

7.

$(−2,0),(3,0),(−5,0) (−2,0),(3,0),(−5,0)$

9.

$(3,0),(−1,0),(0,0) (3,0),(−1,0),(0,0)$

11.

$( 0,0 ),( −5,0 ),( 2,0 ) ( 0,0 ),( −5,0 ),( 2,0 )$

13.

$( 0,0 ),( −5,0 ),( 4,0 ) ( 0,0 ),( −5,0 ),( 4,0 )$

15.

$( 2,0 ),( −2,0 ),( −1,0 ) ( 2,0 ),( −2,0 ),( −1,0 )$

17.

$(−2,0),(2,0),( 1 2 ,0 ) (−2,0),(2,0),( 1 2 ,0 )$

19.

$( 1,0 ),( −1,0 ) ( 1,0 ),( −1,0 )$

21.

$(0,0),( 3 ,0),(− 3 ,0) (0,0),( 3 ,0),(− 3 ,0)$

23.

$( 0,0 ) ( 0,0 )$, $( 1,0 )( 1,0 )$, $( −1,0 )( −1,0 )$, $( 2,0 )( 2,0 )$, $( −2,0 ) ( −2,0 )$

25.

$f( 2 )=–10 f( 2 )=–10$ and $f( 4 )=28. f( 4 )=28.$ Sign change confirms.

27.

$f( 1 )=3 f( 1 )=3$ and $f( 3 )=–77. f( 3 )=–77.$ Sign change confirms.

29.

$f( 0.01 )=1.000001 f( 0.01 )=1.000001$ and $f( 0.1 )=–7.999. f( 0.1 )=–7.999.$ Sign change confirms.

31.

0 with multiplicity 2, $− 3 2 − 3 2$ with multiplicity 5, 4 with multiplicity 2

33.

0 with multiplicity 2, –2 with multiplicity 2

35.

$− 2 3 − 2 3$ with multiplicity $5,55,5$ with multiplicity $2 2$

37.

$0 0$ with multiplicity $4,24,2$ with multiplicity $1,–11,–1$ with multiplicity $1 1$

39.

$3 2 3 2$ with multiplicity 2, 0 with multiplicity 3

41.

$0 0$ with multiplicity $6, 2 3 6, 2 3$ with multiplicity $2 2$

43.

x-intercepts, $( 1, 0 ) ( 1, 0 )$ with multiplicity 2, $( –4, 0 ) ( –4, 0 )$ with multiplicity 1, $y- y-$ intercept $( 0, 4 ) ( 0, 4 )$ . As $x→−∞x→−∞$, $g(x)→−∞g(x)→−∞$, as $x→∞x→∞$, $g(x)→∞g(x)→∞$. 45.

x-intercepts $(3,0) (3,0)$ with multiplicity 3, $(2,0) (2,0)$ with multiplicity 2, $y- y-$ intercept $(0,–108) (0,–108)$. As $x→−∞x→−∞$, $k(x)→−∞k(x)→−∞$, as $x→∞ x→∞$, $k(x)→∞. k(x)→∞.$ 47.

x-intercepts $(0, 0 ), (–2, 0), (4, 0) (0, 0 ), (–2, 0), (4, 0)$ with multiplicity 1, $y y$-intercept $(0, 0). (0, 0).$ As $x→−∞ x→−∞$, $n(x)→∞n(x)→∞$, as $x→∞x→∞$, $n(x)→−∞. n(x)→−∞.$ 49.

$f(x)=− 2 9 (x−3)(x+1)(x+3) f(x)=− 2 9 (x−3)(x+1)(x+3)$

51.

$f(x)= 1 4 (x+2) 2 (x−3) f(x)= 1 4 (x+2) 2 (x−3)$

53.

–4, –2, 1, 3 with multiplicity 1

55.

–2, 3 each with multiplicity 2

57.

$f(x)=− 2 3 (x+2)(x−1)(x−3) f(x)=− 2 3 (x+2)(x−1)(x−3)$

59.

$f(x)= 1 3 (x−3) 2 (x−1) 2 (x+3) f(x)= 1 3 (x−3) 2 (x−1) 2 (x+3)$

61.

$f(x)=−15 (x−1) 2 (x−3) 3 f(x)=−15 (x−1) 2 (x−3) 3$

63.

$f(x)=−2( x+3 )( x+2 )( x−1 ) f(x)=−2( x+3 )( x+2 )( x−1 )$

65.

$f(x)=− 3 2 ( 2x−1 ) 2 ( x−6 )( x+2 ) f(x)=− 3 2 ( 2x−1 ) 2 ( x−6 )( x+2 )$

67.

local max local min

69.

global min

71.

global min

73.

$f(x)= (x−500) 2 (x+200) f(x)= (x−500) 2 (x+200)$

75.

$f(x)=4 x 3 −36 x 2 +80x f(x)=4 x 3 −36 x 2 +80x$

77.

$f(x)=4 x 3 −36 x 2 +60x+100 f(x)=4 x 3 −36 x 2 +60x+100$

79.

$f(x)=9π( x 3 +5 x 2 +8x+4) f(x)=9π( x 3 +5 x 2 +8x+4)$

### 3.5 Section Exercises

1.

The binomial is a factor of the polynomial.

3.

$x+6+ 5 x-1 x+6+ 5 x-1$, quotient: $x+6 x+6$, remainder: $5 5$

5.

$3x+2 3x+2$, quotient:  $3x+2 3x+2$, remainder:  $0 0$

7.

$x−5 x−5$, quotient: $x−5 x−5$, remainder: $0 0$

9.

$2x−7+ 16 x+2 2x−7+ 16 x+2$, quotient: $2x−7 2x−7$, remainder: $16 16$

11.

$x−2+ 6 3x+1 x−2+ 6 3x+1$, quotient: $x−2 x−2$, remainder: $6 6$

13.

$2 x 2 −3x+5 2 x 2 −3x+5$, quotient: $2 x 2 −3x+5 2 x 2 −3x+5$, remainder: $0 0$

15.

$2 x 2 +2x+1+ 10 x−4 2 x 2 +2x+1+ 10 x−4$

17.

$2 x 2 −7x+1− 2 2x+1 2 x 2 −7x+1− 2 2x+1$

19.

$3 x 2 −11x+34− 106 x+3 3 x 2 −11x+34− 106 x+3$

21.

$x 2 +5x+1 x 2 +5x+1$

23.

$4 x 2 −21x+84− 323 x+4 4 x 2 −21x+84− 323 x+4$

25.

$x 2 −14x+49 x 2 −14x+49$

27.

$3 x 2 +x+ 2 3x−1 3 x 2 +x+ 2 3x−1$

29.

$x 3 −3x+1 x 3 −3x+1$

31.

$x 3 − x 2 +2 x 3 − x 2 +2$

33.

$x 3 −6 x 2 +12x−8 x 3 −6 x 2 +12x−8$

35.

$x 3 −9 x 2 +27x−27 x 3 −9 x 2 +27x−27$

37.

$2 x 3 −2x+2 2 x 3 −2x+2$

39.

Yes $( x−2 )(3 x 3 −5) ( x−2 )(3 x 3 −5)$

41.

Yes $( x−2 )(4 x 3 +8 x 2 +x+2) ( x−2 )(4 x 3 +8 x 2 +x+2)$

43.

No

45.

$(x−1)( x 2 +2x+4) (x−1)( x 2 +2x+4)$

47.

$(x−5)( x 2 +x+1) (x−5)( x 2 +x+1)$

49.

Quotient: $4 x 2 +8x+164 x 2 +8x+16$, remainder: $−1 −1$

51.

Quotient: $3 x 2 +3x+53 x 2 +3x+5$, remainder: $0 0$

53.

Quotient: $x 3 −2 x 2 +4x−8 x 3 −2 x 2 +4x−8$, remainder: $−6 −6$

55.

$x 6 − x 5 + x 4 − x 3 + x 2 −x+1 x 6 − x 5 + x 4 − x 3 + x 2 −x+1$

57.

$x 3 − x 2 +x−1+ 1 x+1 x 3 − x 2 +x−1+ 1 x+1$

59.

$1+ 1+i x−i 1+ 1+i x−i$

61.

$1+ 1−i x+i 1+ 1−i x+i$

63.

$x 2 −ix−1+ 1−i x−i x 2 −ix−1+ 1−i x−i$

65.

$2 x 2 +3 2 x 2 +3$

67.

$2x+3 2x+3$

69.

$x+2 x+2$

71.

$x−3 x−3$

73.

$3 x 2 −2 3 x 2 −2$

### 3.6 Section Exercises

1.

The theorem can be used to evaluate a polynomial.

3.

Rational zeros can be expressed as fractions whereas real zeros include irrational numbers.

5.

Polynomial functions can have repeated zeros, so the fact that number is a zero doesn’t preclude it being a zero again.

7.

$−106 −106$

9.

$0 0$

11.

$255 255$

13.

$−1 −1$

15.

$−2,1, 1 2 −2,1, 1 2$

17.

$−2 −2$

19.

$−3 −3$

21.

$− 5 2 , 6 ,− 6 − 5 2 , 6 ,− 6$

23.

$2,−4,− 3 2 2,−4,− 3 2$

25.

$4,−4,−5 4,−4,−5$

27.

$5,−3,− 1 2 5,−3,− 1 2$

29.

$1 2 , 1+ 5 2 , 1− 5 2 1 2 , 1+ 5 2 , 1− 5 2$

31.

$3 2 3 2$

33.

$2,3,−1,−2 2,3,−1,−2$

35.

$1 2 ,− 1 2 ,2,−3 1 2 ,− 1 2 ,2,−3$

37.

$−1,−1, 5 ,− 5 −1,−1, 5 ,− 5$

39.

$− 3 4 ,− 1 2 − 3 4 ,− 1 2$

41.

$2,3+2i,3−2i 2,3+2i,3−2i$

43.

$− 2 3 ,1+2i,1−2i − 2 3 ,1+2i,1−2i$

45.

$− 1 2 ,1+4i,1−4i − 1 2 ,1+4i,1−4i$

47.

1 positive, 1 negative 49.

3 or 1 positive, 0 negative 51.

0 positive, 3 or 1 negative 53.

2 or 0 positive, 2 or 0 negative 55.

2 or 0 positive, 2 or 0 negative 57.

$±5,±1,± 5 2 ±5,±1,± 5 2$

59.

$±1,± 1 2 ,± 1 3 ,± 1 6 ±1,± 1 2 ,± 1 3 ,± 1 6$

61.

$1, 1 2 ,− 1 3 1, 1 2 ,− 1 3$

63.

$2, 1 4 ,− 3 2 2, 1 4 ,− 3 2$

65.

$5 4 5 4$

67.

$f(x)= 4 9 ( x 3 + x 2 −x−1 ) f(x)= 4 9 ( x 3 + x 2 −x−1 )$

69.

$f(x)=− 1 5 ( 4 x 3 −x ) f(x)=− 1 5 ( 4 x 3 −x )$

71.

8 by 4 by 6 inches

73.

5.5 by 4.5 by 3.5 inches

75.

8 by 5 by 3 inches

77.

Radius = 6 meters, Height = 2 meters

79.

Radius = 2.5 meters, Height = 4.5 meters

### 3.7 Section Exercises

1.

The rational function will be represented by a quotient of polynomial functions.

3.

The numerator and denominator must have a common factor.

5.

Yes. The numerator of the formula of the functions would have only complex roots and/or factors common to both the numerator and denominator.

7.

9.

11.

V.A. at $x=– 2 5 ; x=– 2 5 ;$ H.A. at $y=0; y=0;$ Domain is all reals $x≠– 2 5 x≠– 2 5$

13.

V.A. at $x=4,–9; x=4,–9;$ H.A. at $y=0; y=0;$ Domain is all reals $x≠4,–9 x≠4,–9$

15.

V.A. at $x=0,4,−4; x=0,4,−4;$ H.A. at $y=0; y=0;$ Domain is all reals $x≠0,4,–4 x≠0,4,–4$

17.

V.A. at $x=5; x=5;$ H.A. at $y=0; y=0;$ Domain is all reals $x≠5,−5 x≠5,−5$

19.

V.A. at $x= 1 3 ; x= 1 3 ;$ H.A. at $y=− 2 3 ; y=− 2 3 ;$ Domain is all reals $x≠ 1 3 . x≠ 1 3 .$

21.

none

23.

25.

Local behavior: $x→− 1 2 + ,f(x)→−∞,x→− 1 2 − ,f(x)→∞ x→− 1 2 + ,f(x)→−∞,x→− 1 2 − ,f(x)→∞$

End behavior: $x→±∞,f(x)→ 1 2 x→±∞,f(x)→ 1 2$

27.

Local behavior: $x→ 6 + ,f(x)→−∞,x→ 6 − ,f(x)→∞, x→ 6 + ,f(x)→−∞,x→ 6 − ,f(x)→∞,$ End behavior: $x→±∞,f(x)→−2 x→±∞,f(x)→−2$

29.

Local behavior: $x→ 1 3 + ,f(x)→∞,x→ 1 3 − , x→ 1 3 + ,f(x)→∞,x→ 1 3 − ,$ $f(x)→−∞,x→− 5 2 − ,f(x)→∞,x→− 5 2 + f(x)→−∞,x→− 5 2 − ,f(x)→∞,x→− 5 2 +$, $f(x)→−∞ f(x)→−∞$

End behavior: $x→±∞, x→±∞,$ $f(x)→ 1 3 f(x)→ 1 3$

31.

$y=2x+4 y=2x+4$

33.

$y=2x y=2x$

35.

$V.A.x=0,H.A.y=2 V.A.x=0,H.A.y=2$ 37.

$V.A.x=2,H.A.y=0 V.A.x=2,H.A.y=0$ 39.

$V.A.x=−4,H.A.y=2;( 3 2 ,0 );( 0,− 3 4 ) V.A.x=−4,H.A.y=2;( 3 2 ,0 );( 0,− 3 4 )$ 41.

$V.A.x=2,H.A.y=0,(0,1) V.A.x=2,H.A.y=0,(0,1)$ 43.

$V.A.x=−4,x= 4 3 ,H.A.y=1;(5,0);( − 1 3 ,0 );( 0, 5 16 ) V.A.x=−4,x= 4 3 ,H.A.y=1;(5,0);( − 1 3 ,0 );( 0, 5 16 )$ 45.

$V.A.x=−1,H.A.y=1;( −3,0 );( 0,3 ) V.A.x=−1,H.A.y=1;( −3,0 );( 0,3 )$; removable discontinuity (hole) at $( 1,2 )( 1,2 )$ 47.

$V.A.x=4,S.A.y=2x+9;( −1,0 );( 1 2 ,0 );( 0, 1 4 ) V.A.x=4,S.A.y=2x+9;( −1,0 );( 1 2 ,0 );( 0, 1 4 )$ 49.

$V.A.x=−2,x=4,H.A.y=1,( 1,0 );( 5,0 );( −3,0 );( 0,− 15 16 ) V.A.x=−2,x=4,H.A.y=1,( 1,0 );( 5,0 );( −3,0 );( 0,− 15 16 )$ 51.

$y=50 x 2 −x−2 x 2 −25 y=50 x 2 −x−2 x 2 −25$

53.

$y=7 x 2 +2x−24 x 2 +9x+20 y=7 x 2 +2x−24 x 2 +9x+20$

55.

$y= 1 2 x 2 −4x+4 x+1 y= 1 2 x 2 −4x+4 x+1$

57.

$y=4 x−3 x 2 −x−12 y=4 x−3 x 2 −x−12$

59.

27(x - 2) / ((x - 3)² (x + 3)) $y=27 x−2 (x−3) 2 (x+3) y=27 x−2 (x−3) 2 (x+3)$

61.

$y= 1 3 x 2 +x−6 x−1 y= 1 3 x 2 +x−6 x−1$

63.

$y=−6 (x−1) 2 (x+3) (x−2) 2 y=−6 (x−1) 2 (x+3) (x−2) 2$

65.
 $x x$ 2.01 2.001 2.0001 1.99 1.999 $y y$ 100 1,000 10,000 –100 –1,000
 $x x$ 10 100 1,000 10,000 100,000 $y y$ 0.125 0.0102 .001 .0001 .00001

Vertical asymptote $x=2, x=2,$ Horizontal asymptote $y=0 y=0$

67.
 $x x$ –4.1 –4.01 –4.001 –3.99 –3.999 $y y$ 82 802 8,002 –798 –7998
 $x x$ 10 100 1,000 10,000 100,000 $y y$ 1.4286 1.9331 1.992 1.9992 1.999992

Vertical asymptote $x=−4, x=−4,$ Horizontal asymptote $y=2 y=2$

69.
 $x x$ –.9 –.99 –.999 –1.1 –1.01 $y y$ 81 9,801 998,001 121 10,201
 $x x$ 10 100 1,000 10,000 100,000 $y y$ 0.82645 0.9803 .998 .9998

Vertical asymptote $x=−1, x=−1,$ Horizontal asymptote $y=1 y=1$

71.

$( 3 2 ,∞ ) ( 3 2 ,∞ )$ 73.

$(−2,1)∪(4,∞) (−2,1)∪(4,∞)$ 75.

$( 2,4 ) ( 2,4 )$

77.

$( 2,5 ) ( 2,5 )$

79.

$( –1,1 ) ( –1,1 )$

81.

$C(t)= 8+2t 300+20t C(t)= 8+2t 300+20t$

83.

85.

$A(x)=50 x 2 + 800 x . A(x)=50 x 2 + 800 x .$ 2 by 2 by 5 feet.

87.

$A(x)=π x 2 + 100 x . A(x)=π x 2 + 100 x .$ Radius = 2.52 meters.

### 3.8 Section Exercises

1.

It can be too difficult or impossible to solve for $x x$ in terms of $y. y.$

3.

We will need a restriction on the domain of the answer.

5.

$f −1 (x)= x +4 f −1 (x)= x +4$

7.

$f −1 (x)= x+3 −1 f −1 (x)= x+3 −1$

9.

$f −1 (x)=− x−5 3 f −1 (x)=− x−5 3$

11.

$f(x)= 9−x f(x)= 9−x$

13.

$f −1 (x)= x−5 3 f −1 (x)= x−5 3$

15.

$f −1 (x)= 4−x 3 f −1 (x)= 4−x 3$

17.

$f −1 (x)= x 2 −1 2 ,[ 0,∞ ) f −1 (x)= x 2 −1 2 ,[ 0,∞ )$

19.

$f −1 (x)= ( x−9 ) 2 +4 4 ,[ 9,∞ ) f −1 (x)= ( x−9 ) 2 +4 4 ,[ 9,∞ )$

21.

$f −1 (x)= ( x−9 2 ) 3 f −1 (x)= ( x−9 2 ) 3$

23.

$f −1 (x)= 2−8x x f −1 (x)= 2−8x x$

25.

$f −1 (x)= 7x−3 1−x f −1 (x)= 7x−3 1−x$

27.

$f −1 (x)= 5x−4 4x+3 f −1 (x)= 5x−4 4x+3$

29.

$f −1 (x)= x+1 −1 f −1 (x)= x+1 −1$

31.

$f −1 (x)= x+6 +3 f −1 (x)= x+6 +3$

33.

$f −1 (x)= 4−x f −1 (x)= 4−x$ 35.

$f −1 (x)= x +4 f −1 (x)= x +4$ 37.

$f −1 (x)= 1−x 3 f −1 (x)= 1−x 3$ 39.

$f −1 (x)= x+8 +3 f −1 (x)= x+8 +3$ 41.

$f −1 (x)= 1 x f −1 (x)= 1 x$ 43.

$[−2,1)∪[3,∞) [−2,1)∪[3,∞)$ 45.

$[−4,2)∪[5,∞) [−4,2)∪[5,∞)$ 47.

$(–2,0);(4,2);(22,3) (–2,0);(4,2);(22,3)$ 49.

$(–4,0);(0,1);(10,2) (–4,0);(0,1);(10,2)$ 51.

$(–3,−1);(1,0);(7,1) (–3,−1);(1,0);(7,1)$ 53.

$f −1 (x)= x+ b 2 4 − b 2 f −1 (x)= x+ b 2 4 − b 2$

55.

$f −1 (x)= x 3 −b a f −1 (x)= x 3 −b a$

57.

$t(h)= 200−h 4.9 , t(h)= 200−h 4.9 ,$ 5.53 seconds

59.

$r(V)= 3V 4π 3 , r(V)= 3V 4π 3 ,$ 3.63 feet

61.

$n(C)= 100C−25 0.6−C , n(C)= 100C−25 0.6−C ,$ 250 mL

63.

$r(V)= V 6π , r(V)= V 6π ,$ 3.99 meters

65.

$r(V)= V 4π , r(V)= V 4π ,$ 1.99 inches

### 3.9 Section Exercises

1.

The graph will have the appearance of a power function.

3.

No. Multiple variables may jointly vary.

5.

$y=5 x 2 y=5 x 2$

7.

$y=11944 x 3 y=11944 x 3$

9.

$y=6 x 4 y=6 x 4$

11.

$y= 18 x 2 y= 18 x 2$

13.

$y= 81 x 4 y= 81 x 4$

15.

$y= 20 x 3 y= 20 x 3$

17.

$y=10xzw y=10xzw$

19.

$y=10x z y=10x z$

21.

$y=4 xz w y=4 xz w$

23.

$y=40 xz w t 2 y=40 xz w t 2$

25.

$y=256 y=256$

27.

$y=6 y=6$

29.

$y=6 y=6$

31.

$y=27 y=27$

33.

$y=3 y=3$

35.

$y=18 y=18$

37.

$y=90 y=90$

39.

$y= 81 2 y= 81 2$

41.

$y= 3 4 x 2 y= 3 4 x 2$ 43.

$y= 1 3 x y= 1 3 x$ 45.

$y= 4 x 2 y= 4 x 2$ 47.

≈ 1.89 years

49.

≈ 0.61 years

51.

3 seconds

53.

48 inches

55.

≈ 49.75 pounds

57.

≈ 33.33 amperes

59.

≈ 2.88 inches

### Review Exercises

1.

$2−2i 2−2i$

3.

$24+3i 24+3i$

5.

${2+i,2−i} {2+i,2−i}$

7.

$f(x)= (x−2) 2 −9vertex(2,–9),intercepts(5,0);(–1,0);(0,–5) f(x)= (x−2) 2 −9vertex(2,–9),intercepts(5,0);(–1,0);(0,–5)$ 9.

$f(x)= 3 25 ( x+2 ) 2 +3 f(x)= 3 25 ( x+2 ) 2 +3$

11.

300 meters by 150 meters, the longer side parallel to river.

13.

Yes, degree = 5, leading coefficient = 4

15.

Yes, degree = 4, leading coefficient = 1

17.

$Asx→−∞,f(x)→−∞,asx→∞,f(x)→∞ Asx→−∞,f(x)→−∞,asx→∞,f(x)→∞$

19.

–3 with multiplicity 2, $− 1 2 − 1 2$ with multiplicity 1, –1 with multiplicity 3

21.

4 with multiplicity 1

23.

$1 2 1 2$ with multiplicity 1, 3 with multiplicity 3

25.

$x 2 +4 x 2 +4$with remainder 12

27.

$x 2 −5x+20− 61 x+3 x 2 −5x+20− 61 x+3$

29.

$2 x 2 −2x−3 2 x 2 −2x−3$, so factored form is $(x+4)(2 x 2 −2x−3) (x+4)(2 x 2 −2x−3)$

31.

${ −2,4,− 1 2 } { −2,4,− 1 2 }$

33.

${ 1,3,4, 1 2 } { 1,3,4, 1 2 }$

35.

0 or 2 positive, 1 negative

37.

Intercepts $(–2,0)and( 0,− 2 5 ) (–2,0)and( 0,− 2 5 )$, Asymptotes $x=5 x=5$ and $y=1. y=1.$ 39.

Intercepts (3, 0), (-3, 0), and $( 0, 27 2 ) ( 0, 27 2 )$, Asymptotes $x=1,x=–2,y=3. x=1,x=–2,y=3.$ 41.

$y=x−2 y=x−2$

43.

$f −1 (x)= x +2 f −1 (x)= x +2$

45.

$f −1 (x)= x+11 −3 f −1 (x)= x+11 −3$

47.

$f −1 (x)= (x+3) 2 −5 4 ,x≥−3 f −1 (x)= (x+3) 2 −5 4 ,x≥−3$

49.

$y=64 y=64$

51.

$y=72 y=72$

53.

148.5 pounds

### Practice Test

1.

$20−10i 20−10i$

3.

${2+3i,2−3i} {2+3i,2−3i}$

5.

$Asx→−∞,f(x)→−∞,asx→∞,f(x)→∞ Asx→−∞,f(x)→−∞,asx→∞,f(x)→∞$

7.

$f(x)= ( x+1 ) 2 −9 f(x)= ( x+1 ) 2 −9$, vertex $( −1,−9 ) ( −1,−9 )$, intercepts $( 2,0 );( −4,0 );( 0,−8 ) ( 2,0 );( −4,0 );( 0,−8 )$ 9.

60,000 square feet

11.

0 with multiplicity 4, 3 with multiplicity 2

13.

$2 x 2 −4x+11− 26 x+2 2 x 2 −4x+11− 26 x+2$

15.

$2 x 2 −x−4 2 x 2 −x−4$. So factored form is $(x+3)(2 x 2 −x−4) (x+3)(2 x 2 −x−4)$

17.

$− 1 2 − 1 2$ (has multiplicity 2), $−1±i 15 2 −1±i 15 2$

19.

$−2 −2$ (has multiplicity 3), $±i ±i$

21.

$f(x)=2 ( 2x−1 ) 3 ( x+3 ) f(x)=2 ( 2x−1 ) 3 ( x+3 )$

23.

Intercepts $(−4,0),( 0,− 4 3 ) (−4,0),( 0,− 4 3 )$, Asymptotes $x=3,x=−1,y=0 x=3,x=−1,y=0$. 25.

$y=x+4 y=x+4$

27.

$f −1 (x)= x+4 3 3 f −1 (x)= x+4 3 3$

29.

$y=18 y=18$

31.

4 seconds Do you know how you learn best?