How do I substitut 3x+y=2, 4×+y=20?

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2 Answers
iceman
Feb 24, 2018

#(x,y)=(18, -52)#

Explanation:

#3x+y=2# => #y=2-3x#
#4x+y=20#
#4x+2-3x=20#
#x=18#
#y=2-54=-52#
#(x,y)=(18, -52)#

Gav
Feb 24, 2018

#y=-52#
#x=18#

Explanation:

Since #y# is a constant in both equations, you can shift #3x# in #3x+y=2#, so #y=2-3x#.
Then you can just substitute into #4x+y=20#
So #4x+(2-3x)=20#
#x+2=20#
#x=18#
Then substitute into any equation #x=18#
Substituting into first equation,
#y=2-3(18)#
#y=-52#

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