Find $\displaystyle\int x^4\,dx$.
- $5x^5 + C$
- $\dfrac{x^5}{5} + C$
- $x^5 + C$
- $4x^3 + C$
Show answer and solution
Correct answer: B. $\dfrac{x^5}{5} + C$
Power rule for integration: $\displaystyle\int x^n\,dx = \dfrac{x^{n+1}}{n+1} + C$ for $n \neq -1$.
Plug $n = 4$: $\dfrac{x^5}{5} + C$.
Option A is the *derivative* of $x^4$, not the integral. Always check by differentiating your answer.