[xf(x)]′=f(x)+xf′(x) [xf(x)]'=f(x)+xf'(x) [xf(x)]′=f(x)+xf′(x)
[ex22f(x)]′=xex22f(x)+ex22f′(x) ⟹ xf(x)+f′(x) \begin{align*} [e^{\frac{x^2}{2}}f(x)]'&=xe^{\frac{x^2}{2}}f(x)+e^{\frac{x^2}{2}}f'(x) \\ &\implies xf(x)+f'(x) \end{align*} [e2x2f(x)]′=xe2x2f(x)+e2x2f′(x)⟹xf(x)+f′(x)
