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

1 Answer

Jun 6, 2015

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

Using [2] substitute $(-3x+1)$ for $y$ in [1]
[3] $color(white)("XXXX")$ $-x+(-3x+1) = 5$
Simplifying
[4] $color(white)("XXXX")$ $-4x = 4$
[5] $color(white)("XXXX")$ $x = -1$

Using [5] substitute $(-1)$ of $x$ in [1]
[6] $color(white)("XXXX")$ $-(-1) + y = 5$
Simplifying
[7] $color(white)("XXXX")$ $y=4$

Solution is $(x,y) = (-1,4)$

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