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

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

  • 3
    only if $x \neq y$2011-02-04
  • 0
    I.J. Kennedy: Well, the original expression wouldn't have made sense if $x=y$.2011-02-06