TeX джерело:

\left\{ \begin{array}{l}\sqrt[4]{{x + y}} = 3,\\\sqrt[4]{{x - y}} = 1;\end{array} \right.\quad \left\{ \begin{array}{l}{(\sqrt[4]{{x + y}})^4} = {3^4},\\{(\sqrt[4]{{x - y}})^4} = {1^4};\end{array} \right.\quad \left\{ \begin{array}{l}x + y = 81,\\x - y = 1;\end{array} \right.\quad \left\{ \begin{array}{l}2x = 82;\\2y = 80;\end{array} \right.\quad \left\{ \begin{array}{l}x = 41;\\y = 40.\end{array} \right.