Question

solve the following pair of linear equations by the substitution method- 2x - 7y = 1 , 4x + 3y = 15

Answer 1

-2x-7y=1 equation1
4x+3y=15 equation 2
from equation 1
-2x=1+7y
x=1+7y/-2 equation A
on putting the value of x in equation 1
-2×1+7y/-2-7y = 1
2+7y-14y/2=1

2-7y=2
-7y=2-2
-7y=0
y=0
now put the value of y in equation 2
4x+3×0=15
4x+3=15
4x=15-3
4x=12
x=12/4
x=3

Answer 2

-2x-7y=1 equation1

4x+3y=15 equation 2

from equation 1

-2x=1+7y

x=1+7y/-2 equation A

on putting the value of x in equation 1

-2×1+7y/-2-7y = 1

2+7y-14y/2=1

2-7y=2

-7y=2-2

-7y=0

y=0

now put the value of y in equation 2

4x+3×0=15

4x+3=15

4x=15-3

4x=12

x=12/4

x=3