theorem :: DIFF_3:48

for k, x0, x1 being Real
for f being Function of REAL,REAL st ( for x being Real holds f . x = k / (x ^2) ) & x0 <> x1 & x0 <> 0 & x1 <> 0 holds
[!f,x0,x1!] = - ((k / (x0 * x1)) * ((1 / x0) + (1 / x1)))