# Thread: help with this problem...

1. ## 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????

2. 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.

Originally Posted by Candy101

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