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Math Help - help with this problem...

  1. #1
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    Exclamation help with this problem...

    i got this question i know how he got everything else expect the 13


    2x^2+10x+3x-15=100 form this he got=====> 2x^2+13x-115=0

    i know how he got everything else expect for the 13

    i got 2x^2+7x-115=0

    how i got this==> i move over the 100 making it -100 and then i combine the -15 with the -100 and i got==> -115

    and then i minus -3 from 3x and 10==> the 3 and -3 cancel out

    so i got====> 7x by taking away 3 from 10x

    did he just add the 10x and 13x????
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  2. #2
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    A very important concept in solving equation is that if you want do something to the equation, you must do it for BOTH sides so that you won't change the question.

    Quote Originally Posted by Candy101 View Post

    and then i minus -3 from 3x and 10==> the 3 and -3 cancel out
    You are doing 2x^{2}+10x-3x+3x-3x-115=0. You minus altogether 6x on the left ONLY, and this is not "balanced". You didn't do BOTH sides.

    Note that when you said you bring the 100 over so that it becomes -100, you are actually minus 100 on BOTH sides, i.e.

    2x^{2}+10x+3x-15-100=100-100
    2x^{2}+10x+3x-115=0

    Anyway, you shoud just add the 3x and 10x.
    Hope this helps
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