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EXERCISE 4.2 on page 70. Hope you like them and do not forget to like , social share
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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

infinitely many solutions

Write four solutions for each of the following equations:

(i) $2x + y = 7$

(ii) $ \pi x + y = 9$

(iii) $x = 4y$

(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

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

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)

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

Find the value of k, if x = 2, y = 1 is a solution of the equation 2x + 3y = k.

Puttinf x=2 and y=1

$ 4 + 3 =k$

$7=k$

Hence k=7

**Notes**-
**Ncert Solutions** **Assignments**

Class 9 Maths Class 9 Science

Download Linear Equation Ex 4.1 assignment as pdf