7. Given the quadratic function f (x) = AX2 + BX + C, G (x) = λ ax + B (λ≥ 1), when | x | ≤ 1, | f (x) | ≤ 1. (1) it is proved that | a | ≤ 2 (2) Let f (0), f (1), f (- 1) denote g (1), G (- 1) (3) When | x | ≤ 1, it is proved that | g (x) | ≤ 2 λ

7. Given the quadratic function f (x) = AX2 + BX + C, G (x) = λ ax + B (λ≥ 1), when | x | ≤ 1, | f (x) | ≤ 1. (1) it is proved that | a | ≤ 2 (2) Let f (0), f (1), f (- 1) denote g (1), G (- 1) (3) When | x | ≤ 1, it is proved that | g (x) | ≤ 2 λ

(1)f(0)=c,f(1)=a+b+c,f(-1)=a-b+c
According to the meaning of the title, - 1