For the function f (x) defined on the interval D, if ∀ x1, X2 ∈ D, and X1 & lt; X2, there is & nbsp; If f (x 1) ≥ f (x 2), then f (x) is a "non increasing function" on interval D. if f (x) is a "non increasing function" on interval [0,1] and f (0) = L, f (x) + F (l-x) = L, then f (x) ≤ - 2x + 1 holds when x ∈ [0,14]. There are the following propositions: ① ∀ x ∈ [0,1], f (x) ≥ 0; ② when x1, X2 ∈ [0,1] and x1 ≠ X2, f (x 1) ≠ f (x) ③ f (18) ）+F (511) + F (713) + F (78) = 2; 4. When x ∈ [0,14], f (f (x)) ≤ f (x). Where the serial numbers of all propositions that you think are correct are______ ．

For the function f (x) defined on the interval D, if ∀ x1, X2 ∈ D, and X1 & lt; X2, there is & nbsp; If f (x 1) ≥ f (x 2), then f (x) is a "non increasing function" on interval D. if f (x) is a "non increasing function" on interval [0,1] and f (0) = L, f (x) + F (l-x) = L, then f (x) ≤ - 2x + 1 holds when x ∈ [0,14]. There are the following propositions: ① ∀ x ∈ [0,1], f (x) ≥ 0; ② when x1, X2 ∈ [0,1] and x1 ≠ X2, f (x 1) ≠ f (x) ③ f (18) ）+F (511) + F (713) + F (78) = 2; 4. When x ∈ [0,14], f (f (x)) ≤ f (x). Where the serial numbers of all propositions that you think are correct are______ ．

For ①, because f (0) = 1, and f (x) + F (l-x) = L, take x = 0, get f (1) = 0, for ∀ x ∈ [0,1], according to the definition of "non increasing function", we know that f (x) ≥ 0. So ① is correct; for ②, from the definition, when x1, X2 ∈ [0,1] and x1 ≠ X2, f (x1) and f (x2) may be equal