limh→0时{[f(a+h)-f(a)]/h-f'(a)}/h=limh→0时[f(a+h)-f(a)]/(h^2)-limh→0时f'(a)/h=(1/2)limh→0时[f'(a+h)-limh→0时f'(a)/h=(1/2)limh→0时[f'(a+h)-f'(a)]/h=f''(a)/2 还是问问高手吧,我这的知识都忘记了....imh→0时{[f(a+h)-f(a)]/h-f'(a)}/h=limh→0时[f(a+h)-f(a)]/(h^2)-limh→0时f'(a)/h=(1/2)limh→0时[f'(a+h)-limh→0时f'(a)/h=(1/2)limh→0时[f'(a+h)-f'(a)]/h=f''(a)/2计算从第三行开始：=(1/2)limh→0时[f'(a+h)-limh→0时f'(a)/h貌似就不对了吧这的知识都忘记了limh→0时[f(a+h)-f(a)]/(h^2)应该等于多少，我也不太确定