I need help with math - factoring

Kimmy · Posted: Wed Mar 05, 2008 2:44 pm Post subject: I need help with math - factoring

This is brief... but can anyone factor the following:

3a^2 + 12 =

So far I have 3(a^2 + 4), but it isn't simplified. I need help on the next step.

Thanks.

mike · Posted: Wed Mar 05, 2008 2:47 pm Post subject:

a^2+4 = (a+2)(a-2)

fully factored would be

3(a+2)(a-2)
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Kimmy · Posted: Wed Mar 05, 2008 2:51 pm Post subject:

I already tried that. When I solved it, the answer was 3a^2 - 12 not 3a^ + 12

I also tried putting a negative sign before the three, but it doesn't help either.

My teacher expects everyone in my math class to have the answer by tomorrow.

boarderlinefrenzy · Posted: Wed Mar 05, 2008 2:59 pm Post subject:

oh my god.... it's like having flashbacks to Nam.
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Kimmy · Posted: Wed Mar 05, 2008 3:20 pm Post subject:

^

Can anyone figure it out?

I'm normally good at math, especially with factoring, but this is just difficult.. even though it may not seem like it at first.

DeadDisco · Posted: Wed Mar 05, 2008 3:24 pm Post subject:

I'm pretty sure 3(a^2 + 4) is the simplified answer. Unless you want sqaure roots in your answer.
I checked this online factoring site and that was the simplified version they gave too.
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sexinyourcereal · Posted: Wed Mar 05, 2008 3:26 pm Post subject:

crazykiki · Posted: Wed Mar 05, 2008 3:44 pm Post subject:

yup i agree with DeadDisco the final answer is 3(a^2+4)
a^2+4 cannot be factored anymore because it is plus 4 and not minus 4, if it was minus 4 then it would be a difference of squares and would be able to be (a+2)(a-2).
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Kimmy · Posted: Wed Mar 05, 2008 3:53 pm Post subject:

Okay, I see your point now. I think I may have already learned this before.
I'll make that my final answer. Thank you.

seasunsky · Posted: Wed Mar 05, 2008 4:26 pm Post subject:

I haven't done it in a long time, I don't know if this is even where it gets applied, but did you try completing the square?
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Kimmy · Posted: Wed Mar 05, 2008 4:27 pm Post subject:

What do you mean?

electricpearls · Posted: Wed Mar 05, 2008 5:45 pm Post subject:

^the quadratic formula using y=ax+bx+c form... x=-b square root of b^2 - 4ac / 2a or something like that... it is applied when you can't factor the equation using decomposition, inspection, etc.

i don't think what you have is factorable past 3(a^2+4), like DeadDisco said.
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dbee · Posted: Thu Mar 06, 2008 6:05 am Post subject:

DeadDisco · Posted: Thu Mar 06, 2008 11:11 am Post subject:

^I'm pretty sure that doesn't work. I don't really know how to explain how it doesn't though.
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seasunsky · Posted: Thu Mar 06, 2008 3:09 pm Post subject:

no... that's not what completing the square is. You would end up with something in the form (x-a)^2+C. I just forget how to do it.
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electricpearls · Posted: Thu Mar 06, 2008 4:25 pm Post subject:

^oh haha, okay I think it's when you get for example, y=ax^2+bx+c in general form and you use completing the square to get it into standard form.

so like, for example, you have y=x^2-4x+6
so you would go Y=(x^2-4X+4)+6-4 and then that would then be factored so it becomes:

Y=(X-2)^2+2

we did the quadratic formula and completing the square in the same lesson so i tend to mix up the two Embarassed

for the original 3a^2+12, factoring past 3(a^2+4) doesn't work because when you graph it, the roots are non real (it never crosses the x), and i also tried the quadratic formula and the result gives you a negative square root, which renders it unfactorable past 3(a^2+4).

so DeadDisco is 110% right.
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lemons22 · Posted: Sun Mar 16, 2008 4:05 pm Post subject:

^ what you did was completing the square. Happy

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emcee · Posted: Sun Mar 16, 2008 5:22 pm Post subject:

Holy crap, I am soo glad I don't take math anymore haha

electricpearls · Posted: Sun Mar 16, 2008 6:10 pm Post subject:

^^Yep, i know it was, lol. Because seasunsky suggested it.

I should try and remember it though... I have a unit test on quadratics tomorrow Razz

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was a long and dark december,
from the rooftops i remember there was snow,
white snow.