Chapter 5 - Section 5.7 - Negative Exponents and Scientific Notation - Exercise Set - Page 409: 65

$16y^{6}$

Using the laws of exponents, the given expression, $ (2y^3)^4y^{-6} ,$ simplifies to \begin{array}{l}\require{cancel} 2^{1(4)}y^{3(4)}y^{-6} \\\\= 2^{4}y^{12}y^{-6} \\\\= 16y^{12+(-6)} \\\\= 16y^{12-6} \\\\= 16y^{6} .\end{array}