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I have $\frac{2ab}{ab-ac-bc+c^2}$. Of course it's $\frac{2ab}{c^2-ac-bc+ab}$ which is $\frac{2ab}{c^2-c(a+b)+ab}$ but for the latter Wolfram tells me it's not the same as $\frac{2ab}{ab-ac-bc+c^2}$. Why? What's wrong with it?

And I know it probably sounds as newbish as it can but I don't have the slightest idea what's wrong here.

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    @JM: The [first input Sfw states s/he used](http://www.wolframalpha.com/input/?i=%28%28ab-ac-bc%2Bc^2%29-%28c^2-c%28a%2Bb%29%2Bab%29%29) does not involve division like the actual expressions in the question, though a couple of W|A's responses are hilariously dumb.2012-05-07

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The problem is that $c(a+b)$ is being interpreted as a function application. If you put a space after $c$, it works. That underlines the point that you should have included your precise input in the original question.

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    In *Mathematica*, the ambiguity between implied multiplication with parentheses and function application is deftly sidestepped, with brackets being restricted to function application, and parentheses for grouping expressions. I suppose Alpha is poor at talking about its assumptions with the input given...2012-05-07