Khan/khan-exercises — Issue #12273: Solving for a variable - Simplifying by -1?
Author: KhanBugz
Created: 2012-01-27 15:24:02+00:00
State: open
Labels: hard, leopard, safari

Reporter: rstorm@gmail.com

Hello,

I don't see the point in getting a problem wrong if we do not simplify by -1? Couldn't we just do this for every single problem then?
I had a specific problem where the denominator was a negative number and the numerator were all positives. How does that simplify by multiplying the top and bottom by -1? You still would end up with a negative number in the end right?
Here is the exact one I am referring to: my solution was e=5f+17g+1/-7fg. I got it wrong because I didn't multiply the top and bottom by -1. If that is the case and all the top becomes a negative number and the bottom becomes positive wouldn't the end result be a negative number still? Hope this makes sense.

[solving_for_a_variable.html?seed=82&problem=ABC_DEF](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/solving_for_a_variable.html?seed=82&problem=ABC_DEF&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/solving_for_a_variable.html?seed=82&problem=ABC_DEF&debug&activity=%5B%5D)

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