Question 1081211
f(x+h)=1/(x+h)
[(1/(x+h))-(1/x)]/h= using common denominator of x(x+h)
x-(x+h)/h(x^2+xh)=-h/h(x^2+xh)
the hs cancel
-1/(x^2+xh)
as h goes to 0, the result goes to -1/x^2.