How do you solve the system #-2x -8y = 4# and #5x-5y=20#?

1 Answer
Aug 8, 2015

Answer:

#(x,y) = (26/5, -6/5)#
Note: As stated in the comments, this question has been modified. If the original intent was correct (2 equations in 4 variables), no solution is possible.

Explanation:

[1]#color(white)("XXXX")##-2x-8y=4#
[2]#color(white)("XXXX")##5x-5y =20#

Simplifying [1] by dividing by #(-2)#
[3]#color(white)("XXXX")##x+4y = -2#
Simplifying [2] by dividing by #5#
[4]#color(white)("XXXX")##x-y= 4#

Subtract [4] from [3]
[5]#color(white)("XXXX")##5y = -6#
Divide by #5#
[6]#color(white)("XXXX")##y = -6/5#

Substituting #(-6/5)# for #y# in [4]
[7]#color(white)("XXXX")##x - (-6/5) = 4#

[8]#color(white)("XXXX")##x =26/5#