Question

O dobro do quadrado de um número ×menos 72 e igual a 0. Qual e esse número.

Answer 1

$\large\boxed{\begin{array}{l}\rm n\acute umero\longrightarrow x\\\rm quadrado\,do\,n\acute umero\longrightarrow x^2\\\rm dobro\,do\,quadrado\,do\,n\acute umero\longrightarrow 2x^2\\\rm equac_{\!\!,}\tilde ao: 2x^2-72=0\\\underline{\sf soluc_{\!\!,}\tilde ao\!:}\\\rm 2x^2-72=0\div(2)\\\rm x^2-36=0\\\rm x^2=36\\\rm x=\pm\sqrt{36}\\\rm x=\pm6\\\rm S=\{-6,6\}\end{array}}$