令f′(x)=0,得x=k-1,
f′(x)f(x)隨x的變化情況如下:
x | (-∞,k-1) | k-1 | (k-1,+∞) |
f′(x) | - | 0 | + |
f(x) | ↓ | -ek-1 | ↑ |
(Ⅱ)當k-1≤0,即k≤1時,函數(shù)f(x)在區(qū)間[0,1]上單調(diào)遞增,
∴f(x)在區(qū)間[0,1]上的最小值為f(0)=-k;
當0<k-1<1,即1<k<2時,由(I)知,f(x)在區(qū)間[0,k-1]上單調(diào)遞減,f(x)在區(qū)間(k-1,1]上單調(diào)遞增,
∴f(x)在區(qū)間[0,1]上的最小值為f(k-1)=-ek-1;
當k-1≥1,即k≥2時,函數(shù)f(x)在區(qū)間[0,1]上單調(diào)遞減,
∴f(x)在區(qū)間[0,1]上的最小值為f(1)=(1-k)e;
綜上所述f(x)min=
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