Resposta :
Área do quadrado
[tex]\huge\boxed{\boxed{\boxed{\boxed{\sf A=\ell^2}}}}[/tex]
[tex]\boxed{\begin{array}{l}\tt a)~\sf A=20^2=400~cm^2\\\tt b)~\sf A=50^2=2500~cm^2\\\tt c)~\sf \ell=\sqrt{225}\\\sf\ell =15~cm\end{array}}[/tex]
[tex]\huge\boxed{\boxed{\boxed{\boxed{\sf A=\ell^2}}}}[/tex]
[tex]\boxed{\begin{array}{l}\tt a)~\sf A=20^2=400~cm^2\\\tt b)~\sf A=50^2=2500~cm^2\\\tt c)~\sf \ell=\sqrt{225}\\\sf\ell =15~cm\end{array}}[/tex]