SIMULTANEOUS EQUATIONS 1

Solve the following equations by substitution method.

2x - y = 3

x + y = 9

Solution

2x - y = 3----------- (i)

x + y = 9---------- (ii)

from equation (ii)

x + y = 9

x = 9- y ----------(iii)

substitute equation (iii) in (i) above,

2x - y = 3

2(9- y) - y = 3

18 - 2y - y = 3  

18 - 3y = 3 (since -2y – y = -3y)

18- 3 = 3y

15 = 3y

15 = 3y

 3     3

5 = y

From equation (iii)

x = 9- y ----------(iii)

x = 9- 5

 x = 4

Hence x=4 and y=5.

TRY THIS…………………….

Solve the following equations by substitution method.

3x - y = 8

2x + 3y = 42