a)
\sqrt{54}=\sqrt2*\sqrt{27}
\sqrt{123}=\sqrt3*\sqrt{41}
\sqrt{10}^5=\sqrt{10}^3*\sqrt{10}^2
\sqrt{12,5}=\sqrt{1,25}*\sqrt{10}
b)
\sqrt[3]{20}=\sqrt[3]2*\sqrt[3]{10}
\sqrt[3]{295}=\sqrt[3]{5}*\sqrt[3]{59}
\sqrt[3]{0,4}=\sqrt[3]0,1*\sqrt[3]{4}
\sqrt[3]{\frac{16}{21}}=\sqrt[3]{\frac{4}{3}}*\sqrt[3]{\frac{4}{7}}