題目 6. (10 points) Evaluate the infinite sum ∑k=0∞1(k+2)k!\sum_{k=0}^{\infty} \frac{1}{(k+2)k!}k=0∑∞(k+2)k!1 by some manipulations of the Taylor series of f(x)=xexf(x)=xe^xf(x)=xex. 解答
