Second derivative, = [(2-2x) * (1-x) 2+(2x-x2) * 2 * (1-x)]/(1-x) 4.

=[(2-2x)*( 1-x)+(2x-x^2)*2]/( 1-x)^3

=[2-4x+2x^2+4x-2x^2]/( 1-x)^3=2/( 1-x)^3