Hello,
\(\sqrt{x} - \sqrt{y} = (\sqrt[4]{x}+ \sqrt[4]{y} )( \sqrt[4]{x} - \sqrt[4]{y} )=72\\\\
\sqrt[4]{x}- \sqrt[4]{y}=6\\\\
(\sqrt[4]{x}+ \sqrt[4]{y})*6=72\\\\
\sqrt[4]{x}+ \sqrt[4]{y}=12 \\
\sqrt[4]{x}- \sqrt[4]{y}=6 \\\\
2 \sqrt[4]{x}=18==\textgreater\sqrt[4]{x}=9==\textgreater\ x=6561\\
2 \sqrt[4]{y}=6==\textgreater\sqrt[4]{y}=3==\textgreater\ y=81\\\)
Proof:
\(\sqrt[4]{6561} - \sqrt[4]{81} =9-3=6\\\\
\sqrt{6561} - \sqrt{81} =81-9=72\)
