若C202n+6=C20n+2(n∈N*),(2-x)n=a0+a1x+a2x2+…+anxn,则a0-a1+a2+…+(-1)nan=______

2024-11-07 21:04:59
推荐回答(1个)
回答(1):

2n+6=n+2或2n+6=20-(n+2),
∴n=-4(舍),n=4,
(2-x)4=a0+a1x+a2x2+a3x3+a4x4
令x=-1,a0-a1+a2-a3+a4=34=81.
故答案为81