How do you solve the system of equations #4x + y = 7# and #4x - 4y = - 8#?

Question

993 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-11-30T22:45:50

#x = 1# and #y = 3#

Step 1) Solve the first equation for #y#:

#4x - 4x + y = 7 - 4x#

#y = 7 - 4x#

Step 2) Substitute #7 - 4x# for #y# in the second equation and solve for #x#:

#4x - 4(7 - 4x) = -8#

#4x - 28 + 16x = -8#

#20x - 28 = -8#

#20x - 28 + 28 = -8 + 28#

#20x = 20#

#(20x)/20 = 20/20#

#x = 1#

Step 3) Substitute #1# doe #x# in the solution to the equation in Step 1) and calculate #y#:

#y = 7 - 4*1#

#y = 7 - 4#

#y = 3#