问题
选择题
(x+2)6的展开式中x3的系数是( )
A.20
B.40
C.80
D.160
答案
设含x3的为第r+1,
则Tr+1=C6rx6-r•2r,
令6-r=3,
得r=3,
故展开式中x3的系数为C63•23=160.
故选D.
(x+2)6的展开式中x3的系数是( )
A.20
B.40
C.80
D.160
设含x3的为第r+1,
则Tr+1=C6rx6-r•2r,
令6-r=3,
得r=3,
故展开式中x3的系数为C63•23=160.
故选D.