When solving the IBVP questions in section3.2 (e.g. problem3.8 ), I know the way to first write $u=\frac{1} {\sqrt{4kt\pi}} \int_{0}^{\infty}( e^{-\frac{(x-y)^2}{4kt}}-e^{-\frac{(x+y)^2}{4kt}}) g(y) dy$, and solve the integrals by completing the squares. When I solve it I normally need 20-30 minutes to write out the whole thing, however, during tutorial we only have 10 minutes to finish these kinds of questions, are there any simpler ways to solve them?