Question

What is the value of expression?

Answer 1

$Use:a^n\cdot a^m=a^{n+m}\\\\5^{-8}\cdot5^{-4}=5^{-8+(-4)}=5^{-12}\\\\Answer:\boxed{D}$

Answer 2

5 ^ ( - 8 - 4 ) = 5 ^ ( - 12 ) D.