Answer
$$\int x^3e^{x^4}dx=\frac{e^{x^4}}{4}+C$$
Work Step by Step
$$A=\int x^3e^{x^4}dx$$
We set $u=x^4$. We then have $$du=4x^3dx$$ $$x^3dx=\frac{1}{4}du$$
Therefore, $$A=\frac{1}{4}\int e^udu$$ $$A=\frac{e^u}{4}+C$$ $$A=\frac{e^{x^4}}{4}+C$$