Step 1: Move the decimal point from its current position (the black dot) to a position immediately to the right of the first nonzero digit (the red dot).
0.000000004.58
Step 2: We moved the decimal point 9 spaces to the left. Therefore, the exponent on base 10 will be negative 9.Now we know that the:
Mantissa = 4.58
Exponent = -9
So, the solution is:
$$0.00000000458 = \color{blue}{ 4.58} \cdot 10^{ \color{red}{ -9 }}$$