How do you solve #x - 9y = -80# and #2y - 2x = 16# using substitution?

1 Answer
Jim G.
May 27, 2018

#(x,y)to(1,9)#

Explanation:

#x-9y=-80to(1)#

#2y-2x=16to(2)#

#"rearrange equation "(1)" expressing x in terms of y"#

#x=-80+9yto(3)#

#color(blue)"substitute "x=-80+9y" in equation "(2)#

#2y-2(-80+9y)=16#

#2y+160-18y=16#

#-16y+160=16#

#"subtract 160 from both sides"#

#-16y=16-160=-144#

#"divide both sides by "-16#

#y=(-144)/(-16)=9#

#"substitute "y=9" in equation "(3)#

#x=-80+81=1#

#"solution is "(x,y)to(1,9)#
graph{(y-1/9x-80/9)(y-x-8)=0 [-20, 20, -10, 10]}

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