How do you solve 3x - 4y = -30 and 7x + 4y = 10?

Question

2966 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-01-13T13:02:03

The solution for the system of equations is
#color(blue)(x=-2, y=6#

#3x-color(blue)(4y)=-30#.....equation #(1)#
#7x +color(blue)(4y)=10#...........equation #(2)#

Solving by elimination

Adding equations #1# and #2#

#3x-cancelcolor(blue)(4y)=-30#

#7x +cancelcolor(blue)(4y)=10#

#10x = -20#

#x = -20/10#

#color(blue)(x = -2#

Finding #y# from equation #1#:

#3x-4y=-30#

#3 xx (-2) -4y=-30#

#-6 -4y=-30#

#-6 + 30 = 4y#

#24 = 4y#

#color(blue)(y =6#