How do you solve the system 2x = 3 - y2x=3−y and 2y = 12 - x2y=12−x by substitution?

1 Answer
Don't Memorise
May 25, 2015

2x = 3 - y2x=3−y
y = 3 - 2xy=3−2x............equation (1)(1)

2y = 12 - x2y=12−x ........equation (2)(2)

substituting equation (1)(1) in equation (2)(2)
2(3-2x) = 12 - x2(3−2x)=12−x
6 - 4x = 12 - x6−4x=12−x
-6 = 3x−6=3x
x =-2x=−2

finding yy :
y = 3 - 2xy=3−2x , from equation (1)(1)
= 3 - 2(-2)=3−2(−2)
= 3+4 = 7=3+4=7

solutions for the system of equations are
color (blue)(x=-2 and y = 7x=−2andy=7

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