How do you solve the system #2x+7y=3 # and #x = 1-4y# by substitution?

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Answer 1 · 2015-05-24T23:47:24

Try this:
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Answer 2 · 2015-05-24T23:49:19

Substitute the formula for #x# from the second equation into the first equation as follows:

#3 = 2x+7y = 2(1-4y)+7y = 2-8y+7y = 2-y#

Add #y# to both ends to get:

#y + 3 = 2#

Subtract #3 from both sides to get:

#y = -1#

Substitute this value for #y# into the original second equation to find #x#:

#x = 1 - 4y = 1 - 4(-1) = 1+4 = 5#