f(y) = x(x - 1)^2
f'(x) = x'(x - 1)^2 + (x - 1)^2'x
f'(x) = (x - 1)^2 + 2x(x - 1)
f'(x) = x^2 - 2x + 1 + 2x^2 - 2x
f'(x) = 3x^2 - 4x + 1
f'(x) = 0
3x^2 - 4x + 1 = 0
x1 = 1, x2 = 1/3
f(1) = 1(1-1)^2 = 0
f(1/3) = 1/3(1/3 - 1)^2 = 1/3 * (-4/9) = -4/27
ymax = 0
ymin = -4/27
