In this page we have NCERT book Solutions for Class 9th Maths Linear equations in two variables for
EXERCISE 4.2 on page 70. Hope you like them and do not forget to like , social share
and comment at the end of the page.
Question 1
Which one of the following options is true, and why?
$y = 3x + 5$ has
(i) a unique solution
(ii) only two solutions
(iii) infinitely many solutions
Solution
infinitely many solutions
Question 2
Write four solutions for each of the following equations:
(i) $2x + y = 7$
(ii) $ \pi x + y = 9$
(iii) $x = 4y$
Solution
(i) $2x + y = 7$
Taking x =0
y=7
Taking y=0
x= 7/2
Taking x=1
y= 7-2 =5
Taking y=1
x=3
So (0,7) ,( 7/2,0),(1,5) and (3,1) are Four solutions
(ii) $ \pi x + y = 9$
Taking x =0
y=9
Taking y=0
$x= \frac {9}{\pi}$
Taking x=1
$y= 9- \pi$
Taking y=1
$x= \frac {8}{\pi}$
So (0,9) ,($\frac {9}{\pi}$,0) ,(1,$9- \pi$) and ($\frac {8}{\pi}$,1) are Four solutions
(iii) $x = 4y$
Taking x =0
y=0
Taking x=1
y= 1/4
Taking y=1
x=4
Taking x=2
x=1/2
So (0,0) ,( 1,1/4),(4,1) and (2,1/2) are Four solutions
Question 3
Check which of the following are solutions of the equation $x - 2y = 4$ and which are not:
(i) (0, 2)
(ii) (2, 0)
(iii) (4, 0)
(iv) $(\sqrt {2},4 \sqrt {2})$
(v) (1,1)
Solution
i. Putting x=0,y=2
$0 -4 =4$
$-4 \ne 4$
So,This is not the solution
ii. Putting x=2,y=0
$2 -0 =4$
$2 \ne 4$
So,This is not the solution
iii. Putting x=4,y=0
$4 -0 =4$
$4 = 4$
So,This is a solution
iv. Putting $x=\sqrt {2}$,$y=4 \sqrt {2}$
$\sqrt {2} -8 \sqrt {2}=4$
$ 7\sqrt {2} \ne 4$
So,This is not the solution
v. Putting x=1,y=1
$ 1 - 2 =4$
$ -1 \ne 4$
So,This is a solution
Question 4
Find the value of k, if x = 2, y = 1 is a solution of the equation 2x + 3y = k.
Solution
Puttinf x=2 and y=1
$ 4 + 3 =k$
$7=k$
Hence k=7
link to this page by copying the following text
Also Read
- Notes
- Ncert Solutions
- Assignments
Search Our Website
Class 9 Maths
Class 9 Science
Download Linear Equation Ex 4.1 assignment as pdf