I'm having some more trouble: Please help me, a little is very appreciated and a lot of help would be a God-send. Thanks, I love this community and I wish I would have found this place many years ago.

Problem 11:

a^2(b+c)(2b+c)+a(b+c)

I got this far: (b+c)[a^2(2b+c)+a]

Same as problem 12. Doesn't come out with same answer when I plug in values to check.

Problem: 12:

t^3(2r+s)(3r+2s)+t^2(3r+2s)

I got this far: (3r+2s)[t^3(2r+s)+t^2]

If I factor out t, I can check to see if it works. by doing t=5, r=4, s=3 and I get the same answer as the problem originally. However, if I factor out t^2 it makes the answer different...any reason or explanation why?

Problem 13:

(2a+1)(a+3)-(2a+1)(a-3)

I got this far: (2a+1)[(a+3)-(a-3)]

I know this is a difference of squares, but what do I do with it?

Problem 15: 3a(5a+2b)(3a-5b)-9(a^2)(5a+2b)(4a-b)

I got this far: (5a+2b)[3a(3a-5b)-9(a^2)(4a-b)]

No idea where to go with this one.

and Problem 16: 6m(3n-2m)(n+m)+8(m^2)(3n-2m)(n+m)]

I got this far: 3n-2m[(6m)(n+m)+8(m^2)(n+m)]

And tried : n+m(3n-2m)[6m+8(m^2)]

Same as before, no idea where to go either.

Any help would be appreciated.

Thanks