How do you solve the system of equations #-2x - 2y = 20# and #x + 2y = - 15#?

Question

788 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-12-04T20:20:49

#x =-5 and y = -5#

This is the best possible scenario for a system of equations, because the y-terms are additive inverses. The sum of additive inverses is always 0.

#" "-2x-2y = +20# ....................................A
#" "x+2y = -15# .....................................B

#A+B: " "-x " "= 5" "larr# no y term. Solve for x

#" ":.x = -5#

Substitute #x = -5# intp either equation .... let's use B

#" "(-5)+2y = -15#

#" "+2y = -15 +5#

#" "+2y = -10#

#" "+y = -5#

#x =-5 and y = -5#