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The fraction:

$\frac{y^2-x^2}{x-y}$

should simplify to the answer:

$-(x+y)$

but the best I could do was expand it to:

$\frac{(y+x)(y-x)}{x-y}$

What's next step?

1 Answers 1

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For $x \neq y$, $\frac{(y+x)(y-x)}{x-y} = \frac{(y+x)(y-x)}{-(y-x)}$

$ = -(y+x)$ $ = -(x+y)$

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    I.J. Kennedy: Well, the original expression wouldn't have made sense if $x=y$.2011-02-06