Solution
= Solution
The kernel has an <integrable singularity> at the moving endpoint $t=x$. Direct substitution into the ordinary <Leibniz integral rule> would produce the undefined boundary value $h(x)/\sqrt{x-x}$ and the nonintegrable differentiated kernel $-h(t)/[2(x-t)^{3/2}]$. Those separately divergent expressions cannot be treated as ordinary finite terms. The <derivative of an Abel integral> is obtained by rewriting the <integral> before differentiating.