How do you solve by substitution x - y = 6 and x + y = -2?

1 Answer
Jun 7, 2015

x-y=6
Thus color(blue)(x=6+y ( we add y on both side )

Now that we have color(blue)x, we can replace it in the second equation :

color(blue)x+y=-2
color(blue)(6+y)+y=-2
6+2y=-2
2y=-2-6 ( we substract 6 on each side )
2y=-8
color(red)(y=-4 ( we divide by 2 on each side )

Now that we have color(red)y, we can find color(blue)x :

color(blue)x=6+color(red)y
color(blue)x=6 color(red)(-4)
color(blue)(x=2)