Two antiderivatives and their constant difference

You are given that $I=\displaystyle\int x(1-x)^{1/2}\,dx$.

(i) Use integration by parts to find an expression for $I$.

(ii) Use the substitution $u^2=1-x$ to find another expression for $I$.

(iii) Show algebraically that your answers to parts (i) and (ii) differ by a constant.