How do you solve x+5y=-3x+5y=3 and 3x-2y=83x2y=8 using substitution?

1 Answer
Feb 12, 2017

See the entire simplification process below:

Explanation:

Step 1) Solve the first equation for xx:

x + 5y = -3x+5y=3

x + 5y - color(red)(5y) = -3 - color(red)(5y)x+5y5y=35y

x + 0 = -3 - 5yx+0=35y

x = -3 - 5yx=35y

Step 2) Substitute -3 - 5y35y for xx in the second equation and solve for yy:

3x - 2y = 83x2y=8 becomes:

3(-3 - 5y) - 2y = 83(35y)2y=8

(3 xx -3) - (3 xx 5y) - 2y = 8(3×3)(3×5y)2y=8

-9 - 15y - 2y = 8915y2y=8

-9 - 17y = 8917y=8

color(red)(9) - 9 - 17y = color(red)(9) + 89917y=9+8

0 - 17y = 17017y=17

-17y = 1717y=17

(-17y)/color(red)(-17) = 17/color(red)(-17)17y17=1717

(color(red)(cancel(color(black)(-17)))y)/cancel(color(red)(-17)) = -1

y = -1

Step 3) Substitute -1 for y in the solution to the first equation at the end of Step 1 and calculate x:

x = -3 - 5y becomes:

x = -3 - (5 xx -1)

x = -3 - (-5)

x = -3 + 5

x = 2

The solution is: x = 2 and y = -1 or (2, -1)