How do you solve the system x + 4y = 28 and - x + 4y = 20?

1 Answer
Alan P.
Jun 14, 2015

(x,y) = (4,6)

Explanation:

[1]color(white)("XXXX")x+4y = 28
[2]color(white)("XXXX")-x+4y = 20

adding [1] and [2]
[3]color(white)("XXXX")8y = 48
dividing by 8
[4]color(white)("XXXX")y = 6

substituting 6 for y (from [4]) in [1]
[5]color(white)("XXXX")x +4(6) = 28
simplifying
[6]color(white)("XXXX")x = 4

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