If f(x)=2x^2-3x+1, find the simplified expression for g(x) in
g(x)= f(2x).
It most certainly is.
Multiply your $\displaystyle a$ and $\displaystyle c$ values. In this case you get $\displaystyle 8$.
So you need to think of two numbers that multiply to give $\displaystyle 8$ and add to give $\displaystyle -6$ (the $\displaystyle b$ value). In this case they are $\displaystyle -4$ and $\displaystyle -2$, which is what you break the middle term into.