@ -360,7 +360,7 @@ $$f'(\xi) = \frac{a+b}{2\eta} f'(\eta)$$
>[!example] 例3
设 $0 < a < b$,证明存在 $\xi \in (a, b)$,使得:
$$f(b)-f(a) = \frac{3\xi^2}{a^2+ab+b^2} f'(\xi)(b-a)$$
$$f(b) - f(a) = \frac{f'(\xi)}{3\xi^2} \cdot (b - a)(a^2 + ab + b^2)$$
**解析**:
将等式变形为: