>>754
|f(b)-f(a)|
=|∫{0,1}f'(t*b+(1-t)*a)*(b-a)dt|
≦∫{0,1}|f'(t*b+(1-t)*a)*(b-a)|dt
≦∫{0,1}|f'(t*b+(1-t)*a)|*|b-a|dt
≦∫{0,1}M|b-a|dt
= M|b-a|