$$\begin{aligned}\int_{a}^{b} e^{-u^{2}} d u &=\int_{a}^{0} e^{-u^{2}} d u+\int_{0}^{b} e^{-u^{2}} d u=\int_{0}^{b} e^{-u^{2}} d u-\int_{0}^{a} e^{-u^{2}} d u \\&=\frac{\sqrt{\pi}}{2} \operatorname{erf}(b)-\frac{\sqrt{\pi}}{2} \operatorname{erf}(a)=\frac{\sqrt{\pi}}{2}[\operatorname{erf}(b)-\operatorname{erf}(a)]
\end{aligned}$$