据题意,f′(1)=tan=1, ∴-3+2a=1,即a=2.
(Ⅱ)由(Ⅰ)知f(x)=-x3+2x2-4,
则f′(x)=-3x2+4x.
X
-1
(-1,0)
0
(0,1)
1
f′(x)
-7
-
+
f(x)