Khan/khan-exercises — Issue #13850: Solving for a variable - Simplyfing by multiplying a -1
Author: KhanBugz
Created: 2012-02-15 00:45:36+00:00
State: open
Labels: chrome, win7, wrong-or-unclear

Reporter: kevinjtobin@gmail.com

I don't understand why multiplying the top and bottom by -1 is "simplifying" anything. The top and bottom of this fraction were both positive. I don't know why we multi.'d by -1 when it seemed perfectly fine the way it was. The -1 makes the first number negative on both the top and bottom. I don't get it. I've watched the videos and they all make sense. This does not.

[solving_for_a_variable.html?seed=45&problem=ABCD_EF](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/solving_for_a_variable.html?seed=45&problem=ABCD_EF&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/solving_for_a_variable.html?seed=45&problem=ABCD_EF&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5C%22None%20of%20the%20above.%5C%22%22%2C320%5D%2C%5B%22hint-activity%22%2C%220%22%2C29%5D%2C%5B%22hint-activity%22%2C%220%22%2C34%5D%2C%5B%22hint-activity%22%2C%220%22%2C36%5D%2C%5B%22hint-activity%22%2C%220%22%2C38%5D%2C%5B%22hint-activity%22%2C%220%22%2C39%5D%2C%5B%22hint-activity%22%2C%220%22%2C44%5D%2C%5B%22hint-activity%22%2C%220%22%2C55%5D%2C%5B%22hint-activity%22%2C%220%22%2C64%5D%5D)

["None of the above."]

Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.75 Safari/535.7

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