How do you solve the system using the elimination method for 9x - 9y = 27 and 7y - 3x = -11?

1 Answer
Jul 9, 2015

Answer:

#(x,y) = (5/2, -1/2)#

Explanation:

[1]#color(white)("XXXX")##9x-9y=27#
[2]#color(white)("XXXX")##7y-3x = -11#

Resequence the terms of [2] so the variables occur in the same order as in [1]
[3]#color(white)("XXXX")##-3x+7y = -11#

Multiply [3] by #3#
[4]#color(white)("XXXX")##-9x+21y = -33#

Add [1] and [4]
[5]#color(white)("XXXX")##12y = -6#

Divide [5] by# 12#
[6]#color(white)("XXXX")##y = -1/2#

Substitute #y=-1/2# into [1]
[7]#color(white)("XXXX")##9x-9(-1/2) = 27#

Simplifying
[8]#color(white)("XXXX")##9x = 45/2#

[9]#color(white)("XXXX")##x = 5/2#