On the problem of binomial theorem: in the 99 th power expansion of (a + b), the term with the smallest coefficient is?

On the problem of binomial theorem: in the 99 th power expansion of (a + b), the term with the smallest coefficient is?

a^99、b^99

Exercises of binomial theorem
Let (1-x + 2x ^ 2) ^ n = A0 + A1 x + A2 x ^ 2 +. + A2N x ^ 2n find a1 + A2 +... A2N

By the condition, (x ^ 2) ^ (N-5) * (1 / x) ^ 5 = x = > n = 8
Let x = 1, then A0 + A1 + +a2n=2^n=2^8=256,
Let x = 0, then A0 = 1,
The answer is 255

It is known that the constant term in the (x-ax) 8 expansion is 1120, where the real number a is a constant, then the sum of the coefficients in the expansion is______ ．

TR + 1 = C8R · x8-r ·(- AX-1) r = (- a) rc8r · x8-2r. Let 8-2r = 0, х r = 4. х (- a) 4c84 = 1120, х a = ± 2. When a = 2, let x = 1, then the sum of expansion coefficients is (1-2) 8 = 1. When a = - 2, let x = 1, then the sum of expansion coefficients is (1 + 2) 8 = 38 = 6561