若(3x+1)5=ax5+bx4+cx3+dx2+ex+f,则a-b+c-d+e-f的值是( ) A.32 B.-32 C.1024 D.-1024
问题描述:
若(3x+1)5=ax5+bx4+cx3+dx2+ex+f,则a-b+c-d+e-f的值是( )
A. 32
B. -32
C. 1024
D. -1024
答
∵(3x+1)5=ax5+bx4+cx3+dx2+ex+f
当x=-1时,有(-2)5=-a+b-c+d-e+f=-32,
∴a-b+c-d+e-f=32,
故选A.