[tex]T=\sqrt[4]{\frac{x^4+y^4}{x^{-4}+y^{-4} } } \\\\T=\sqrt[4]{\frac{x^4+y^4}{\frac{x^4+y^4}{x^4y^4} } } \\\\T = \sqrt[4]{x^4y^4}\\\\ T = xy[/tex]
