How do solve the following linear system?: # x+y=-4, 3x – 4y = 7 #?

1 Answer
Dec 6, 2015

Answer:

The solution for the system of equations is
#color(blue)(x=-9/7 , y=-19/7#

Explanation:

#color(blue)(3x)-4y = 7#.........equation #(1)#

#x+y=-4#, multiplying this equation by #3#
#color(blue)(3x) +3y = -12#....equation #(2)#

Solving by elimination

Subtracting equation #2# from #1# results in elimination of #color(blue)(3x#

#cancelcolor(blue)(3x)-4y = 7#
#-cancelcolor(blue)(3x) -3y = +12#

#-7y=19#

#y=19/(-7)#

#color(blue)(y=-19/(7)#

Finding #x# by substituting #y# in equation #2#:
#x+y=-4#

#x=-4-y#

#x=-4-(-19/7)#

#x=-4+19/7#

#x=-28/7+19/7#

#color(blue)(x=-9/7#