If 2x^2 - 2y^2 = 72 and if x+y=18 what does x-y equal

Question

David Figueroa

Mathematics

18 December, 05:18

If 2x^2 - 2y^2 = 72 and if x+y=18 what does x-y equal

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Answers (2)

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Tatum Rowe · Answer 1

2x^2-2y^2=72

divide both sides by 2

x^2-y^2=36

factor difference of 2 perfect squares

(x-y) (x+y) = 36

given that x+y=18, subsitute 18 for x+y

(x-y) (18) = 36

divide both sides by 18

x-y=2

Harley Jackson · Answer 2

First factor out the 2:

x^2 - y^2 = 36

x^2 - y^2 can be factored into (x+y) (y-y) so:

(x + y) (x - y) = 36

plug in your value:

18 (x-y) = 36 and you should be able to take it from there