I can quite grasp what is going on here. Can your bright minds please shine a little light my way. I do understand the first 2 but I don't know how they came about with the last two.
You appear to be saying that you know that [tex](x^a)^b= x^{ab}[tex] so that [tex](x^{p+1})^2(x^{p-1})^2= (x^{2(p+1)})(x^{2(p-1)})[tex].
Do not know that $\displaystyle x^{a}x^{b}= x^{a+ b}$? $\displaystyle x^{2(p-1)+ 2(p+1)}= x^{2p- 2+ 2p+ 2}$.