Hi, I am from Poland so please forgive my english.

I seem to have problems solving the following assignment (translated)

"There are polynomials:

P(x) = (2x+1)^3

Q(x) = 8x+a

R(x) = 4x^2-1

S(x) = 8x^2 +cx

Whataandcis required for P(x) + Q(x) - 3R(x) = S(x)?"

After many conversions, I came up with this:

(2x+1)^3 +a= 12x^2 - 3 +cx

But after that I have no idea what next, plus I may not even be heading the right direction... help?