Answer
$8.4\times10^{-4}$
Work Step by Step
We are given the number $.00084$.
Step 1: To write this number in scientific notation, we move the decimal point to the right until the original number is 8.4.
Step 2: Since the original number was less than 1, we moved the decimal by 4 negative places. In other words, we will raise 10 to a power of -4.
Now, we write the product of the two numbers found in Step 1 and Step 2.
$8.4\times10^{-4}$