={[f(x_0+h)-f(x_0)]/h+[f(x_0)-f(x_0-h)]/h}/5
=[f'(x_0)+f'(x_0)]/5
=2/5*f'(x_0)
---------
或者直接洛必达
=[f'(x_0+h)+f'(x_0-h)]/5
=2/5*f'(x_0)
={[f(x_0+h)-f(x_0)]/h+[f(x_0)-f(x_0-h)]/h}/5
=[f'(x_0)+f'(x_0)]/5
=2/5*f'(x_0)
---------
或者直接洛必达
=[f'(x_0+h)+f'(x_0-h)]/5
=2/5*f'(x_0)