1.
2f(x) + f(1-x) = x^2
把1-x代入
2f(1-x) + f(x) = (1-x)^2
两式解出
f(x) = (2x^2 - (1-x)^2)/3 = (x^2 + 2x - 1)/3
2.
都不是.定义域不对称.