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Power antiderivative

Reverse the power rule to find an antiderivative.

Calculus · Integration
$$\int x^n\,dx=\frac{x^{n+1}}{n+1}+C$$

Power antiderivative is one of 7 integration formulas in the calculus section of this library, and it is used at ap · university level.

Why power antiderivative works

Differentiating x to the n+1 hands back n+1 times x to the n, so dividing by n+1 cancels that unwanted factor and returns exactly the function you started with. The constant is there because sliding a graph up or down never changes any of its slopes.

What each symbol means

$n$ is constant and $C$ represents every constant antiderivative.

Power antiderivative: when it holds

$n\ne-1$; when $n=-1$, use $\int dx/x=\ln|x|+C$.

When it stops applying

An exponent of −1 breaks it outright, because n+1 becomes 0 and the rule asks you to divide by zero. The antiderivative of 1 over x is the natural logarithm of |x| plus a constant, which is not a power at all.

Power antiderivative: a worked example

$\int x^3dx=x^4/4+C$.

The mistake to avoid

What people do: Leaving the constant of integration off an indefinite integral.

Why it goes wrong: Every function of that form plus any constant has the same derivative, so an answer without the constant names only one member of an infinite family.

Do this instead: Write the constant the moment the integral is done. In a differential equation it is exactly what the initial condition pins down.

Power antiderivative: step by step

  1. Name the unknown, and the unit the answer has to come out in.
  2. Match the symbols to your values. $n$ is constant and $C$ represents every constant antiderivative.
  3. Check the conditions before substituting. $n\ne-1$; when $n=-1$, use $\int dx/x=\ln|x|+C$.
  4. Substitute, keep exact values to the last line, then test the sign, size, and unit against a rough estimate — the check that catches most calculus slips.

Where this formula fits

Subject
Calculus formulas — 42 entries in this library
Topic
Integration
Level
AP · University

Formulas are easiest to keep when they sit inside a method rather than on a list. Use the links below to see where power antiderivative comes from, to check a calculation against a tool, and to practise it until you can recall it without looking.

Questions about power antiderivative

Does the rule handle a square root?

Yes. Write the root as the one half power, raise it to three halves, and divide by three halves, giving two thirds of x to the three halves.

How do I integrate a plain number like 7?

Treat it as 7 times x to the zero. The exponent climbs to 1 and you divide by 1, so the antiderivative is 7x plus a constant.

Why does the exponent climb here when a derivative sends it down?

Integration runs the derivative backwards, so every step reverses: add one to the exponent rather than subtracting, and divide rather than multiply.

Can two different-looking answers both be right?

Yes, as long as they differ only by a constant. Differentiating both is the quickest way to confirm that they describe the same family.

Stuck on a problem?

Work a power antiderivative problem step by step

Type your own problem, or upload a photo of it. You get the method, the answer, and a check you can repeat yourself.