Let n be a positive integer. Find the continuous functions f:ℝ->ℝ with the property that integral from 1 to x of f(ln(t)) dt=x^n ln(x) for all positive real numbers x.
Differentiating the integral equation with respect to x we obtain: f(ln(x))=nxn-1ln(x)+xn-1=xn-1=xn-1(nln(x)+1), for any positive real number x.Let ln(x)=t, thus x=etand f(t)=et(n-1)(nt+1), for any t>0