Explanation: 
Another Explanation (5): ```html
সমাধান
ধরি, \(u = x^4\)
তাহলে, \(\frac{du}{dx} = 4x^3\)
সুতরাং, \(dx = \frac{du}{4x^3}\)
এখন, \(\int x^3 e^{x^4} dx = \int x^3 e^u \frac{du}{4x^3}\)
\( = \frac{1}{4} \int e^u du\)
\( = \frac{1}{4} e^u + c\)
যেহেতু \(u = x^4\), তাই
\( = \frac{1}{4} e^{x^4} + c\)
অতএব, \(\int x^3 e^{x^4} dx = \frac{1}{4} e^{x^4} + c\) 🎉
```