[tex]\underline{\ \ \ \ \ \ 123}\\1\ \ \ |15129\\\underline{\ \ \ \ \|1}\\22\ |\ 51\\\underline{\ \ \ \ |\ 44}\\243|\ \ 729\\\underline{\ \ \ \ \ |\ 729}\\.\qquad\ \ \ 0[/tex]
[tex]\sqrt{15129}=123[/tex]
[tex]\begin{array}{c|c}15129&3\\5043&3\\1681&41\\41&41\\1\end{array}15129=3\cdot3\cdot41\cdot41=3^2\cdot41^2\\\\\sqrt{15129}=\sqrt{3^2\cdot41^2}=\sqrt3^2}\cdot\sqrt{41^2}=3\cdot41=123[/tex]
[tex]Used:\\\\\sqrt{a\cdot b}=\sqrt{a}\cdot\sqrt{b}\\\\\sqrt{a^2}=a\ for\ a\geq0[/tex]