[tex]\mathcal{A} = \ell^2 =49 \Longrightarrow \ell^2 = 7^2 \Longrightarrow \ell =7\ cm
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[tex]\mathcal{A} = \ell^2 =6,25 \Longrightarrow \ell^2 = 2,5^2 \Longrightarrow \ell =2,5\ cm [/tex]
[tex]\mathcal{A} = \ell^2 =9,61 \Longrightarrow \ell^2 = 3,1^2 \Longrightarrow \ell =3,1\ cm[/tex]