Chapter 22, Problem 14P

There is no closed form solution for the error function,

$\text{erf}\left(a\right)=\frac{2}{\sqrt{\pi }}{\displaystyle {\int }_0^a{e}^{-x^2}}dx$

Use the two-point Gauss quadrature approach to estimate $\text{erf}\left(1.5\right)$.

Note that the exact value is 0.966105.