Calculus: Other Calculus Problems – #144

Question: Let $$f\left( x \right)=\sum\limits_{n=0}^{\infty }{\frac{{{\left( -1 \right)}^{n}}{{2}^{n}}{{x}^{n}}}{n!}}$$. Show that $$f”\left( x \right)=4f\left( x \right)$$.