How do you solve this system of equations using the substitution method #x- y = 4 and 6x + 4y = - 66#?

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Answer 1 · 2017-10-19T04:07:40

#y=-9, x=-5#

#x-y=4 rArr# equation 1
#6x+4y=-66 rArr# equation 2

Make either #x# or #y# the subject of equation 1, so you can substitute the values of in into equation 2.

#x=4+y#

Substitute this into equation 2.

#6(4+y)+4y=-66#
#24+6y+4y=-66#
#10y=-90#
#:.y=-9#

To find #x#, substitute #y=-9# back into either equation 1 or 2.

#x-(-9)=4#
#x=4-9#
#:.x=-5#