How can I make the larger integration sign without using this $$...$$
Since I have written that
$(Uu)(x,y)=\dfrac{1}{\Gamma(r_1)\Gamma(r_2)} \int\limits_0^x \int\limits_0^y \dfrac{F(x,y,s,t,u(s,t))}{(x-s)^{1-r_1}(y-t)^{1-r_2}}dt\;ds,$
but the output integration is looking small so I want to make large integration without using $$....$$ so please help me.
$$ <math> $$is obsolete in LaTeX, but you can use$\displaystyle <math> $– Johannes_B Sep 07 '14 at 18:07