How do you solve the system x = −2y − 1x=−2y−1 and 2x + y = −202x+y=−20?

1 Answer
Alan P.
May 27, 2015

Given
"[1] "x=-2y-1[1] x=−2y−1
"[2] "2x+y = -20[2] 2x+y=−20

We can substitute for xx in [2] the expression for xx in [1]
"[3] "2(-2y-1)+y = -20[3] 2(−2y−1)+y=−20
Simplifying
"[4] "-3y -2 = -20[4] −3y−2=−20
which implies
[5] "y=6[5]y=6

Substituting the value for yy back into [1]
"[6] "x = -2(6) -1[6] x=−2(6)−1
implying
"[7] "x = -13[7] x=−13

Solution is (x,y) = (-13,6)(x,y)=(−13,6)

Related questions
See all questions in Systems Using Substitution
Impact of this question
4984 views around the world
You can reuse this answer
Creative Commons License