[tex]a)\frac{-2}{\sqrt{5} -7} \cdot\frac{\sqrt{5}+7 }{\sqrt{5} +7} =-\frac{2(\sqrt{5} +7)}{(\sqrt{5} -7)(\sqrt{5} +7)} =-\frac{\not2(\sqrt{5} +7)}{\not-44} =\boxed{\frac{\sqrt{5}+7 }{22} }[/tex]
[tex]b)\frac{4}{\sqrt[3]{2} } \cdot\frac{\sqrt[3]{2^2} }{\sqrt[3]{2^2} } =\frac{4\sqrt[3]{2^2} }{\sqrt[3]{2\cdot2^2} } =\frac{\not4\sqrt[3]{2^2} }{\not2} =2\sqrt[3]{2^2} =\boxed{2\sqrt[3]{4} }[/tex]
