NCERT Solution for Linear equation Chapter 4 Exercise 4.2

In this page we have linear equations in two variables class 9 ncert solutions 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

Summary

Linear equations in two variables class 9 ncert solutions Exercise 4.2 has been prepared by Expert with utmost care. If you find any mistake.Please do provide feedback on mail.

This chapter 4 has total 4 Exercise 4.1 ,4.2,4.3 and 4.4. This is the second exercise in the chapter.You can explore previous exercise of this chapter by clicking the link below