hi, some more matrices problems that i can't solve

no 1 :

a) Find PQ which i did =

i can't solve b which is

b) Find a matrix X such that PX + Q = P

no2) If work out $\displaystyle x^{2}$ and $\displaystyle X ^{3}$

hence show that $\displaystyle X^{3} = 4X - X^{2} + I$

i worked out x^2 and X^3 , and i tried doing the above calculations but didn't get x^3

what should i do?

thanks in advance