 Two-node Gaussian quadrature with linear weight

For weight $w(x)=x$ on $[0,1]$, the two-node Gaussian quadrature nodes are roots of $x^2-6x/5+3/10$, the monic quadratic orthogonal to all linear polynomials. Its weights come from integrating the Lagrange interpolation cardinal functions. Orthogonality gives exactness on cubic polynomials and positive weights.