What value of x maximizes F when Solution rather integrating it first and then using derivative simply use Leibnitz rule here of differentiation 1/[(x+4)2 + 3] - 1/[x2 + 3] put value of upper limitin integrand and multipy it with diferentiation of upper limit w.r.t variable \'x\' minus , put value of lower limit in integrand multiply by differntaition of lower limit w.r.t variable \'x\' as written above expression (x2 + 3) - (x+4)2 - 3 = 0 -16 - 8x = 0 x = -2 answer !!!! you can check whether it is maximum or minimum at x =-2 using second derivative I am not doing it here ......