Solve the following equations by substitution method i) 2x – 7y = 3

1.	Solve the following equations by substitution method i) 2x – 7y = 3 ii) 4x + y = 21
Answer» The given two linear equations are 2x – 7y = 3 …………. (1) 4x + y = 21 …………..(2) From the equation (2) we get y = 21 – 4x now we substitute this Y value in equation (1) We get 2x – 7(21 – 4x) = 3 ⇒ 2x- 147 + 28 x – 3 ⇒ 30 x = 147 + 3 = 150 then x = 150/30 ∴ x = 5 Now put x = 5 in equation (2) we get 4(5) + y = 21 20 + y = 21 y = 21 – 20 = 1 So x = 5 and y = 1 are the solutions of the system.

Solve the following equations by substitution method i) 2x – 7y = 3 ii) 4x + y = 21

Answer»

The given two linear equations are

2x – 7y = 3 …………. (1)

4x + y = 21 …………..(2)

From the equation (2) we get

y = 21 – 4x now we substitute this Y

value in equation (1)

We get

2x – 7(21 – 4x) = 3

⇒ 2x- 147 + 28 x – 3

⇒ 30 x = 147 + 3 = 150

then x = 150/30 ∴ x = 5

Now put x = 5 in equation (2) we get

4(5) + y = 21

20 + y = 21

y = 21 – 20 = 1

So x = 5 and y = 1 are the solutions of the system.