How do you solve the system #y-x=-1, x+y=8#?

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Answer 1 · 2016-11-27T20:05:46

{x,y}={4.5,3.5}

#y-x=-1" "(1)#

#x+y=8" "(2)#

#"the sum of left sides of equations (1) ,(2)"#

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

#"the sum of right sides of equations (1),(2)"#

#-1+8=7#

#2y=7#

#y=7/2=3.5#

#"now use (1) or (2)"#

#3.5-x=-1#

#x=3.5+1=4.5#