Respuesta :
let's recall that the conjugate of say a + b is simply the same thing with a different sign in between, namely a - b, so let's use the conjugate of the denominator and multiply top and bottom by it.
[tex]\textit{difference of squares} \\\\ (a-b)(a+b) = a^2-b^2 \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \cfrac{4+\sqrt{2}}{2-\sqrt{2}}\cdot \cfrac{2+\sqrt{2}}{2+\sqrt{2}}\implies \cfrac{(4+\sqrt{2})(2+\sqrt{2})}{\underset{\textit{difference of squares}}{(2-\sqrt{2})(2+\sqrt{2})}}\implies \cfrac{(4+\sqrt{2})(2+\sqrt{2})}{2^2-(\sqrt{2})^2}[/tex]
[tex]\cfrac{8+4\sqrt{2}+2\sqrt{2}+(\sqrt{2})^2}{4-2}\implies \cfrac{8+4\sqrt{2}+2\sqrt{2}+2}{2}\implies \cfrac{10+6\sqrt{2}}{2} \\\\\\ \cfrac{~~\begin{matrix} 2 \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~(5+3\sqrt{2})}{~~\begin{matrix} 2 \\[-0.7em]\cline{1-1}\\[-5pt]\end{matrix}~~}\implies \boxed{5+3\sqrt{2}}[/tex]
