1, let f(x) = ax 2+bx+c (a ≠ 0), replace f (x) with 2x+ 1 and 2x- 1, and then use f (2x+1)+f (.

2. let the radical number x+ 1=t, then X = (T- 1) 2, f (t) = (t-1) 2+2 (t-1) = t 2-65438.

3. -x generations are used on both sides of the equation to form a binary linear equation group, and f(x) can be obtained by addition and subtraction.