Thom6666

$f''(1)=Lim\frac{f'(1+h))-f'(1)}{h} ; khi h \mapsto 0; Vi :f'(1+h) = Lim\frac{f(1+h-h)-f(1+h)}{-h} Taco : VT = Lim\frac{\frac{f(1+h-h)-f(1-h)}{-h}-\frac{f(1+h)-f(1)}{-h}}{-h}= VP(dpcm)$