How do you solve by substitution: y=-x+5 and 3x-y=-1?

1 Answer
Alan P.
Oct 1, 2015

Substitute the expression given for y by the first equation for y in the second equation and simplify to get
#(x,y)=(1,4)

Explanation:

[1]color(white)("XXX")y=-x+5
[2]color(white)("XXX")3x-y=-1

Substituting (-x+5) from [1] into [2] in place of y
[3]color(white)("XXX")3x-(-x+5) = -1

Simplifying
[4]color(white)("XXX")4x-5 = -1

[5]color(white)("XXX")4x = 4

[6]color(white)("XXX")x=1

Substituting 1 for x
[7]color(white)("XXX")y =- 1+5

[8]color(white)("XXX")y=4

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