We start by writing the expression in ax^b form:
[tex]\begin{gathered} (2x^{-7})^4 \\ 2^4\cdot x^{-7\cdot4} \\ 16x^{-28} \end{gathered}[/tex]Now, we have the expression is 16x^(-28), so a = 16 and b = -28.
If we add them, we get:
[tex]a+b=16+(-28)=16-28=-12[/tex]Answer: the sum of a and b is -12.