Step-by-step explanation:
[tex] \sf \hookrightarrow \: {n}^{2} = 20 \\ \sf \hookrightarrow \: \sqrt{ {n}^{2} } = \sqrt{20} \\ \sf \hookrightarrow \: n = \sqrt{20} \\ \star \bf \: n = 2 \sqrt{5} \\ \\ \sf \hookrightarrow \: {a}^{2} = 90 \\ \sf \hookrightarrow \: \sqrt{ {a}^{2} } = \sqrt{90} \\ \sf \hookrightarrow \: a = \sqrt{90} \\ \star \bf \: a = 3 \sqrt{10} [/tex]
