Answer
$-2.0\times10^{15}$
Work Step by Step
Step 1: Scientific Notation includes only one non-zero digit in front of the decimal point.
Step 2: For $-2,000,000,000,000,000.0$, the decimal point must be moved 15 times to the left in order to ensure that their is only one non-zero digit in front of the decimal point.
Step 3: Therefore, $-2,000,000,000,000,000.0=-2.0\times10^{15}$.
