Chapter 7 - Exponents and Exponential Functions - 7-3 Multipying Powers with the Same Base - Practice and Problem-Solving Exercises - Page 429: 16

$8t^{-8}$

We start with the given expression: $4t^{-5}\times2t^{-3}$ We rearrange and regroup the expression using the associative and commutative properties of multiplication: $(4\times2)(t^{-5}t^{-3})$ We multiply the coefficients: $8(t^{-5}t^{-3})$ To multiply powers with the same base, we add the exponents: $8(t^{-5+(-3)})=8t^{-8}$