Answer
We can not use the properties discussed in this section to simplify the given expression.
Work Step by Step
We are asked to simplify (if possible):
$\sqrt{3}*\sqrt{-4}$
Recall the property (pg. 367):
$\sqrt[n]{a}\cdot \sqrt[n]{b}=\sqrt[n]{ab}$ (if $\sqrt[n]{a}$ and $\sqrt[n]{b}$ are real numbers)
We see that $\sqrt{-4}$ is not a real number (it is imaginary because $x^2\ne -4$ for any real value of $x$). Thus we can not apply any of the properties discussed in this section to simplify the given expression.