[tex]\bf ~~~~~~~~~~~~\textit{negative exponents}
\\\\
a^{-n} \implies \cfrac{1}{a^n}
\qquad \qquad
\cfrac{1}{a^n}\implies a^{-n}
\qquad \qquad
a^n\implies \cfrac{1}{a^{-n}}
\\\\
-------------------------------\\\\
\cfrac{3.9\times 10^5}{1.3\times 10^2}\implies \cfrac{3.9}{1.3}\times \cfrac{10^5}{10^2}\implies 3\times 10^5\cdot 10^{-2}\implies 3\times 10^{5-2}
\\\\\\
3\times 10^3\implies 3.0\times 10^3[/tex]
