scientific notation simply means, leave only an integer to the left-side of the dot and use power of 10 for the amount.
[tex] \bf 0\underline{.000004}9\implies 4.9\times 10^{-6}\impliedby \begin{array}{llll} \textit{we moved the dot 6 slots}\\ \textit{to the right, so }10^{-6} \end{array} [/tex]
