13. Express $\frac{x^{3}+2}{(x-1)^{4}}$ as partial fractions.
(Hint: Let $x^{3}+2=[(x-1)+1]^{3}+2=(x-1)^{3}$ $+3(x-1)^{2}+3(x-1)+3$. The answer is: $\frac{1}{x-1}+$ $\left.\frac{3}{(x-1)^{2}}+\frac{3}{(x-1)^{3}}+\frac{3}{(x-1)^{4}}.\right)$