(-4 x 10^-6) (2 x 10^4) =?

The first step in multiplying numbers in scientific notation is to group the constants and the powers of 10

(-4 X 2)(10^{-6} X 10^{4})

Now that they are regrouped, we can multiply the constants and add the powers of ten. This produces an answer is scientific notation.

-8 X 10^{-2}

To change an expression in scientific notation into standard notation, move the decimal point the number of places equal to the exponent on the 10. If it is negative, the decimal point moves to the left. For this problem, we are moving the decimal point 2 places to the left.

-.08