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Help with equation

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Help with equation

by anniev2 » Wed Mar 11, 2009 7:29 am
Here is a solution to an equation however I would have solved it differently and incorrectly for that matter.

Correct:
–x – 1 = 2x – 1
0 = 3x
0 = x

Why does my method not yield the same result:
–x – 1 = 2x – 1
–x = 2x – 1 + 1
–x = 2x

From here I would think that both sides should be divided by x or by -1 but that is obviously incorrect.
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Re: Help with equation

by DanaJ » Wed Mar 11, 2009 8:14 am
anniev2 wrote:
Why does my method not yield the same result:
–x – 1 = 2x – 1
–x = 2x – 1 + 1
–x = 2x

From here I would think that both sides should be divided by x or by -1 but that is obviously incorrect.
Well, so you get that:
-x = 2x - add x to each side to get:
0 = 3x.

So your solution is correct, but you shouldn't divide both sides by x. If you do that, you get that:
-1 = 2 - which is obviously FALSE.
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by zephir21 » Wed Mar 11, 2009 8:15 am
In fact it does match ;)

-x = 2x
0 = 2x + x
0 = 3x .....

So you got it right
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by anniev2 » Wed Mar 11, 2009 1:33 pm
I see where I went wrong...

I thought that whenver a variable is alone on the side of an equation that it should be divided. However now I understand that if the variable was being added or subtracted to begin with then it should be added or subtracted for elimination.

Is this correct?
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