Integration Power Rule
Quick overview of the integration power rule.
Main Idea
The integration power rule is
\[\int x^n\,dx=\frac{x^{n+1}}{n+1}+C,\]as long as
\[n\ne -1.\]This mainly reverses the derivative power rule, where we add 1 to the power and divide by that new power.
Watch this section: introduction at 0:00.
Example 1: A Single Power Of $x$
A simple example of this rule in action follows
\[\int x^5\,dx.\]Here the exponent is $5$. Add $1$ to the exponent:
\[5+1=6.\]Then divide by the same new exponent:
\[\int x^5\,dx=\frac{x^6}{6}+C.\]Watch this section: example 1 at 0:45.
Example 2: Use The Rule Term By Term
Let’s move onto examples where we have more than one expression/term added together within our integral. How do we apply this rule then?
The idea is:
\[\int \left(\text{term 1}+\text{term 2}+\text{term 3}\right)dx =\int (\text{term 1})dx+\int (\text{term 2})dx+\int (\text{term 3})dx.\]You treat each term as an individual integral and apply the power rule for each term.
Watch this section: example 2 at 1:15.
The n Equals Negative 1 Exception
What happens when the power is $-1$? ($n=-1$)
Well
\[n+1=-1+1=0.\]The term $x^{-1}$ is the same as $\frac{1}{x}$, and it uses its own antiderivative:
\[\int \frac{1}{x}\,dx=\int x^{-1}\,dx=\ln\lvert x\rvert+C.\]So the power rule handles powers like $x^5$, $x^4$, $x^2$, and $x^{-2}$, but the special power $x^{-1}$ becomes a natural logarithm.
Watch this section: the $n=-1$ case at 3:20.
Timestamp Guide
Related Calculus Work
This rule is the integration-side partner to the derivative power rule. For derivative practice, use the power rule derivative examples.
Because the answers are indefinite integrals, every result needs $+C$. For the reason behind that constant, review the constant of integration notes.
You can also continue with u-substitution or the full JoeCMath integration playlist.