How do you solve the system of equations #-7x + 2y = 7# and #y = 3x#?

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Answer 1 · 2017-03-27T16:07:24

See the entire solution process below:

Step 1) Because the second equation is already solved for #y#, substitute #3x# for #y# in the first equation and solve for #x#:

#-7x + 2y = 7# becomes:

#-7x + 2(3x) = 7#

#-7x + 6x = 7#

#(-7 + 6)x = 7#

#-1x = 7#

#color(red)(-1) xx -1x = color(red)(-1) xx 7#

#1x = -7#

#x = -7#

Step 2) Substitute #-7# for #x# in the second problem and calculate #y#:

#y = 3x# becomes:

#y = 3 xx -7#

#y = -21#

The solution is: #x = -7# and #y = -21# or #(-7, -21)#