How do you solve the following system: #4x+3y= -1 , x-y=3 #?

1 Answer
Apr 3, 2018

Answer:

#x=8/7" or " 1 1/7color(white)("xxxx")y=-13/7" or " -1 6/7#

Explanation:

Given
[1]#color(white)("XXX")4x+3y=-1#
[2]#color(white)("XXX")x-y=3#

Re-arranging [2]
[3]#color(white)("XXX")x=y+3#

Substituting #(y+3)# for #x# in [1]
[4]#color(white)("XXX")4(y+3)+3y=-1#

Expanding and simplifying the lefts side of [4]
[5]#color(white)("XXX")7y+12=-1#

Subtracting #12# from both sides of [5]
[6]#color(white)("XXX")7y=-13#

Dividing both sides of [6] by 7
[8]#color(white)("XXX")y=-13/7#

Substituting #(-13/7)# for #y# in [3]
[9]#color(white)("XXX")x=-13/7+3=(-13+21)/7=8/7#