assuming you want to simplify
your question looks like this: [tex] \sqrt[8y]{ x^{16} } [/tex]
remember the exponential law that says
[tex] x^{ \frac{m}{n} }= \sqrt[n]{ x^{m} } [/tex] so therefor
[tex] \sqrt[8]{ 8y^{16} } [/tex] = [tex] 8y^{ \frac{16}{8} } [/tex]
simplify the fraction
16/8=2/1=2
[tex] 8y^{ \frac{16}{8} } [/tex]=[tex] 8y^{2} [/tex]
