Question

Solve the given system of linear equations for y: 4x + y = -11 and x + 2y = -8

Answer 1

4x+y=-11
y=-11-(4x)

x+2y=-8
2y=-8-x
y=(-8-x)/2

y=-11-4(-8-2y)
y=-11-(32-8y)
y=-11+32+8y
y=21+8y
0=21+8y-y
0=21+7y
-21=7y
y=-3

Answer 2

4x + y = -11
4x - 4x + y = -11 - 4x
y = -11 - 4x
4x - 11 - 4x = -11
4x - 4x - 11 = -11
0x - 11 = -11
+11 +11
0x = 0
0 0
x = 0
4(0) + y = -11
0 + y = -11
+0 +0
y = -11
(x, y) = (0, -11)

x + 2y = -8
x - x + 2y = -8 - x
2y = -8 - x
2 2
y = -4 - 1/2x
x + 2(-4 - 1/2x) = -8
x - 8 - x = -8
x - x - 8 = -8
0x - 8 = -8
+8 +8
0x = 0
0 0
x = 0
0 + 2y = -8
+0 +0
2y = -8
2 2
y = -4
(x, y) = (0, -4)