Algebra

Question

+1

893

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If $x-y=15$ and $xy=4$, what is the value of $x^2+y^2$?

AbooshAndrew Dec 28, 2018

Rom · Answer 1 · 2018-12-28T04:04:17

$(x-y)^2 = (x^2 + y^2) - 2xy\\ x^2 + y^2 = (x-y)^2 + 2xy = \\ 225+8 = 233$

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CoolStuffYT · Answer 2 · 2018-12-28T12:59:21

$(x-y)^2=(x^2+y^2)-2xy$

Substituting our given numbers,

$15^2=(x^2+y^2)-2(4), 225=(x^2+y^2)-8, x^2+y^2=233$

You are very welcome!

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