## Need help with Factoring

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.
diane123
Posts: 2
Joined: Sun Oct 04, 2015 7:06 pm
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### Need help with Factoring

I need help with this problem:
63n^3+54n^2-105n-90

I don't understand the answer... when I tried to solve it, this is what I did:

(63n^3+54n^2)-(105n-90)
9n^2(7n+6)-3(35n+30) I am stuck here, I don't know what to do, the numbers in the ( )s are not the same... I don't know what to do next. I don't understand how from here the answer is 3(3n^2-5)(7n+6).

little_dragon
Posts: 226
Joined: Mon Dec 08, 2008 5:18 pm
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### Re: Need help with Factoring

I need help with this problem:
63n^3+54n^2-105n-90

I don't understand the answer... when I tried to solve it, this is what I did:

(63n^3+54n^2)-(105n-90)
b/c of the "-" in front of the parens this should be (63n^3 + 54n^2) - (105n + 90)
9n^2(7n+6)-3(35n+30) I am stuck here,
when it doesnt work one way, try it w/ a different grouping
they're right that 3 comes out of everything so start w/ that: 3(21n^3 + 18n^2 - 35n - 30)
then try pairing the other way: (21n^3 - 35n) + (18n^2 - 30)
then factor: 7n(3n^2 - 5) + 6(3n^2 - 5)
etc etc
btw it would work ur way if u factor out a 5: 9n^2(7n + 6) - 3*5(7n + 6)
Last edited by little_dragon on Tue Oct 06, 2015 1:20 pm, edited 1 time in total.

diane123
Posts: 2
Joined: Sun Oct 04, 2015 7:06 pm
Contact:

### Re: Need help with Factoring

Oh wow, thank you so much! How do I know to pair 21n^3 with 35n and 18n^2 with -30?

little_dragon
Posts: 226
Joined: Mon Dec 08, 2008 5:18 pm
Contact:

### Re: Need help with Factoring

Oh wow, thank you so much! How do I know to pair 21n^3 with 35n and 18n^2 with -30?
u dont
like i said: if it doesnt work 1 way, try a different way
see what happens