Numerical Quadrature
Show that there is no set of nodes \(x_1,x_2,\ldots ,x_n\) and coefficients \(\alpha _1,\alpha _2,\ldots ,\alpha _n\) such that the quadrature rule \[ \sum _{j=1}^n \alpha _j f(x_j) \] exactly equals to the integral \(\int _a^b f(x)w(x)dx\) for all polynomials \(f(x)\) of degree less than or equal to \(2n\). \(w(x)\) is the weight function.