Q. \[ \int 3^{x}\,dx \]

Answer

We use the rule \(\int a^x\,dx=\dfrac{a^x}{\ln a}+C\) for \(a>0\), \(a\ne 1\). Here \(a=3\).

\[
\int 3^x\,dx=\frac{3^x}{\ln 3}+C
\]

Detailed Explanation

We want to compute the indefinite integral

\[
\int 3^{x}\,dx
\]

Step 1: Recall the rule for integrating an exponential of the form \(a^{x}\).

A standard result is:

\[
\int a^{x}\,dx=\frac{a^{x}}{\ln(a)}+C \quad \text{for } a>0,\ a\neq 1
\]

Here, \(a=3\), so \(\ln(3)\) will appear in the denominator.

Step 2: Substitute \(a=3\) into the formula.

\[
\int 3^{x}\,dx=\frac{3^{x}}{\ln(3)}+C
\]

Step 3: (Optional check by differentiating.)

Differentiate the result:

\[
\frac{d}{dx}\left(\frac{3^{x}}{\ln(3)}\right)=\frac{1}{\ln(3)}\cdot \frac{d}{dx}\left(3^{x}\right)
\]

Using \(\frac{d}{dx}\left(3^{x}\right)=3^{x}\ln(3)\):

\[
\frac{1}{\ln(3)}\cdot \left(3^{x}\ln(3)\right)=3^{x}
\]

This matches the integrand, so the answer is correct.

Final Answer:

\[
\int 3^{x}\,dx=\frac{3^{x}}{\ln(3)}+C
\]

See full solution
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Calculus FAQ

What is \( \int 3^x\,dx \)?

\(\int 3^x\,dx=\dfrac{3^x}{\ln 3}+C\).

How do you use the rule \(\int a^x\,dx\) with \(a=3\)?

Use \(\int a^x\,dx=\dfrac{a^x}{\ln a}+C\). For \(a=3\), \(\int 3^x\,dx=\dfrac{3^x}{\ln 3}+C\).

Why does a \(\ln 3\) appear in the answer?

Because \(\dfrac{d}{dx}\left(3^x\right)=3^x\ln 3\). Dividing by \(\ln 3\) gives the antiderivative.

What is \( \int 5^x\,dx \)?

\(\int 5^x\,dx=\dfrac{5^x}{\ln 5}+C\).

What is \( \int 2\cdot 3^x\,dx \)?

Pull out the constant: \(\int 2\cdot 3^x\,dx=2\int 3^x\,dx=\dfrac{2\cdot 3^x}{\ln 3}+C\).

What is \( \int 3^{2x}\,dx \)?

Rewrite as \(3^{2x}=(3^2)^x=9^x\). Then \(\int 3^{2x}\,dx=\dfrac{9^x}{\ln 9}+C=\dfrac{3^{2x}}{2\ln 3}+C\).
Try this integral with 3^x steps.
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