For which of the following functions is f(x) = f(1-x) for all x?
f(x) = 1-x
f(x) = 1-x^2
f(x) = x^2 - (1-x^2)
f(x) = x^2(1-x)^2
f(x) = x/1-x
f(x) = 1-x
f(x) = 1-x^2
f(x) = x^2 - (1-x^2)
f(x) = x^2(1-x)^2
f(x) = x/1-x
