Chapter 7 - Exponents and Exponential Functions - 7-3 Multipying Powers with the Same Base - Practice and Problem-Solving Exercises - Page 430: 39

$2^{-3}\times2^{4}=2^{1}$

$2^?\times2^4=2^{1}$ To multiply powers with the same base, we add the exponents. When we add $4$ and the first exponent, we must get $1$. The only way this is true is if the first exponent is $-3$. Therefore, $2^{-3}\times2^{4}=2^{1}$