How do you solve the following linear system: x+8y=3, 4x+5y=-2 x+8y=3,4x+5y=2?

1 Answer
Apr 30, 2017

See the solution process below:

Explanation:

Step 1) Solve the first equation for xx:

x + 8y = 3x+8y=3

x + 8y - color(red)(8y) = 3 - color(red)(8y)x+8y8y=38y

x + 0 = 3 - 8yx+0=38y

x = 3 - 8yx=38y

Step 2) Subsitute 3 - 8y38y for xx in the second equation and solve for yy:

4x + 5y = -24x+5y=2 becomes:

4(3 - 8y) + 5y = -24(38y)+5y=2

(4 * 3) - (4 * 8y) + 5y = -2(43)(48y)+5y=2

12 - 32y + 5y = -21232y+5y=2

12 + (-32 + 5)y = -212+(32+5)y=2

12 - 27y = -21227y=2

-color(red)(12) + 12 - 27y = -color(red)(12) - 212+1227y=122

0 - 27y = -14027y=14

-27y = -1427y=14

(-27y)/color(red)(-27) = (-14)/color(red)(-27)27y27=1427

(color(red)(cancel(color(black)(-27)))y)/cancel(color(red)(-27)) = 14/27

y = 14/27

Step 3) Substitute 14/27 for y in the solution to the first equation at the end of Step 1 and calculate x:

x = 3 - 8y becomes:

x = 3 - (8 * 14/27)

x = 3 - 112/27

x = (3 * 27/27) - 112/27

x = 81/27 - 112/27

x = -31/27

The solution is: x = -31/27 and y = 14/27 or (-31/27, 14/27)