Answer
$\dfrac{x^4}{2}$
Work Step by Step
The area for a right triangle is given by:
$A=\dfrac{\text{length} \times \text{width}}{2}$
where $A$ is the area.
We are given that the width is $x$ and the length is $x^3$.
Thus, we have:
$A(x)=\dfrac{(x^3)( x)}{2}=\dfrac{x^4}{2}$
