Find the quadratic that interpolates f(x) = 2x3 - x + 1 at the nodes x0 = 0, x1 = 2, x2 = 3,
a) by solving a set of three equations for the coefficients of p2(x) = a2x2 + a1x + a0.
b) by using Lagrange's approach.
From b) find the sum of the three coefficient polynomials lk(x), k = 0, 1, 2.