[tex] \sqrt[16]{a ^{16} } = a[/tex]
[tex] \sqrt[3]{27x^{27} } = 3 x^{9} [/tex]
[tex] \sqrt{64x ^{6} } = 8x^{3} [/tex]
[tex] \sqrt[3]{64 x^{6} } = 4 x^{2} [/tex]
[tex] \sqrt[3]{0.001x^{3} } = 0.1x[/tex]
[tex] \sqrt[4]{81x ^{4} } = 3x[/tex]
[tex] \sqrt[5]{729a ^{2} } = 3 \sqrt[5]{3a ^{2} } [/tex]
Last expression is not clear :-(
Note: You must memorize the perfect squares and perfect cubes, or learn the technique finding the roots by continuous division.