Find the first four nonzero terms in the Legendre series of the function

f(x) = 0, for -1<=x<=0

f(x) = x, for 0<=x<=1

Using a plotting program/graphing software, plot over the interval −1 ≤ x ≤ 1 the graph of the function f (x) and of the function g(x) equal to the first four nonzero terms of the Legendre series. [If you do not have a graphing program/calculator whose output you can print, you may go online to obtain one.]