设u = ∫[0→1] ƒ(x) dx
ƒ(x) = x - u,两边取对x的积分,0 ≤ x ≤ 1
u = ∫[0→1] (x - u) dx
u = (x²/2 - ux) |[0→1]
u = 1/2 - u
2u = 1/2 → u = 1/4
所以ƒ(x) = x - 1/4
设u = ∫[0→1] ƒ(x) dx
ƒ(x) = x - u,两边取对x的积分,0 ≤ x ≤ 1
u = ∫[0→1] (x - u) dx
u = (x²/2 - ux) |[0→1]
u = 1/2 - u
2u = 1/2 → u = 1/4
所以ƒ(x) = x - 1/4