How do you solve the system of equations x- 7y = 21x−7y=21 and 2x - 7y = 282x−7y=28?

1 Answer
hev1
Mar 26, 2018

x = 7x=7 and y = -2y=−2

Explanation:

x-7y = 21x−7y=21
2x - 7y = 282x−7y=28

Subtracting the second equation from the first equation:
2x - 7y - (x - 7y) = 28-212x−7y−(x−7y)=28−21
2x - 7y -x + 7y = 72x−7y−x+7y=7
x = 7x=7

Plugging in 77 for xx in the first equation:
7-7y = 217−7y=21
7 = 21 + 7y7=21+7y
7y = 7-217y=7−21
7y = -147y=−14
y = -14/7y=−147
y = -2y=−2

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