How do you solve #x + y = -4# and #y = -3x + 2# using substitution?

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Answer 1 · 2017-07-12T17:51:58

#(x,y)=(-3,-7)#

#x+y=-4--(1)#

#y=-3x+2--(2)#

substitute for y from #(2)" "#into #" "(1)#

#x+ -3x+2=-4#

#-2x=-4-2#

#=>x=3#

substitute into #(1)# to find #y#
https://socratic.org/
#3+y=-4#

#=>y=-7#

#:.(x,y)=(3,-7)#

a quick mental check for #eqn(2)# will see that the solution is consistent.