Question

Use addition to solve the linear system of equations. Include all of your work in your final answer.
{x - y = 4
{x + 2y = 4



WRITER

Answer 1

We have
(1) x − y = 4
(2) x + 2y = 4

To eliminate x, multiply (1) by −1 and add it to (2):

−(1): −x + y = −4
add (2): x + 2y = 4
-------------------
3y = 0

So y = 0. Substitute y = 0 into (1):

x − 0 = 4 ⇒ x = 4.

Solution: (x, y) = (4, 0). (Check: 4 + 2·0 = 4.)