Answer
$8$
Work Step by Step
Note that:
$4^{1.5}=4^{\frac{3}{2}}$
Since $2^2=4$, then:
$4^{\frac{3}{2}}=(2^2)^{\frac{3}{2}}$
Now, recall the basic exponent property (pg. 360):
$(a^m)^n=a^{mn}$
Applying this property, we get:
\begin{align*}
(2^2)^{\frac{3}{2}}&=2^{\frac{2\cdot 3}{2}}\\
&=2^{\frac{6}{2}}\\
&=2^{3}\\
&=8\end{align*}