若A-B=2,A-C=I/2,则(B-C)的3次方-3(B-C)+9/4=?

A-B=2, <1>
A-C=I/2, <2>
<2>- <1>
B-C=--3/2
(B-C)的3次方-3(B-C)+9/4
=(-3/2)^3-3(-3/2)+9/4
=0