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If $p(x+y)^2=5$ and $q (x-y)^2=3$, then the simplified value of $p^2(x+y)^2+4pqxy-q^2(x-y)^2$ is?

Answer: $2(p+q)$

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    $\begingroup$ We already have $$(x+y)^2,(x-y)^2$$ Can't you find $xy$ from there? $\endgroup$ Jul 10, 2017 at 11:47

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$$(x+y)^2 = 5/p$$

$$(x-y)^2 = 3/q$$

$$\implies 4xy = 5/p - 3/q$$

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we have $$5p-3q+pq(\frac{5}{p}-\frac{3}{q})=2p+2q=2(p+q)$$

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