Question

Solve each system by substitution. Show all work.
4x + y = 0
-x - 2y =7

Answer 1

4x + y = 0

-x - 2y =7

with - x - 2y = 7

we have x = -2y - 7

we replace x by this value in the first one

4 * (-2y - 7) + y = 0

- 8y - 28 + y = 0

- 7y = 28

y = 28/(-7)

y = - 4

since 4x + y = 0

we have 4x + (-4) = 0

4x = 4

x = 1

(1 ; -4)