Calculus Examples

$x^{2} \ln (x)$

Step 1

Find the first derivative.

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Step 1.1

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x^{2}$ and $g (x) = \ln (x)$ .

$x^{2} \frac{d}{d x} [\ln (x)] + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.2

The derivative of $\ln (x)$ with respect to $x$ is $\frac{1}{x}$ .

$x^{2} \frac{1}{x} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3

Differentiate using the Power Rule.

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Step 1.3.1

Combine $x^{2}$ and $\frac{1}{x}$ .

$\frac{x^{2}}{x} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.2

Cancel the common factor of $x^{2}$ and $x$ .

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Step 1.3.2.1

Factor $x$ out of $x^{2}$ .

$\frac{x \cdot x}{x} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.2.2

Cancel the common factors.

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Step 1.3.2.2.1

Raise $x$ to the power of $1$ .

$\frac{x \cdot x}{x^{1}} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.2.2.2

Factor $x$ out of $x^{1}$ .

$\frac{x \cdot x}{x \cdot 1} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.2.2.3

Cancel the common factor.

$\frac{x \cdot x}{x \cdot 1} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.2.2.4

Rewrite the expression.

$\frac{x}{1} + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.2.2.5

Divide $x$ by $1$ .

$x + \ln (x) \frac{d}{d x} [x^{2}]$

Step 1.3.3

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 2$ .

$x + \ln (x) (2 x)$

Step 1.3.4

Reorder terms.

$f' (x) = 2 x \ln (x) + x$

Step 2

Find the second derivative.

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Step 2.1

By the Sum Rule, the derivative of $2 x \ln (x) + x$ with respect to $x$ is $\frac{d}{d x} [2 x \ln (x)] + \frac{d}{d x} [x]$ .

$\frac{d}{d x} [2 x \ln (x)] + \frac{d}{d x} [x]$

Step 2.2

Evaluate $\frac{d}{d x} [2 x \ln (x)]$ .

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Step 2.2.1

Since $2$ is constant with respect to $x$ , the derivative of $2 x \ln (x)$ with respect to $x$ is $2 \frac{d}{d x} [x \ln (x)]$ .

$2 \frac{d}{d x} [x \ln (x)] + \frac{d}{d x} [x]$

Step 2.2.2

Differentiate using the Product Rule which states that $\frac{d}{d x} [f (x) g (x)]$ is $f (x) \frac{d}{d x} [g (x)] + g (x) \frac{d}{d x} [f (x)]$ where $f (x) = x$ and $g (x) = \ln (x)$ .

$2 (x \frac{d}{d x} [\ln (x)] + \ln (x) \frac{d}{d x} [x]) + \frac{d}{d x} [x]$

Step 2.2.3

The derivative of $\ln (x)$ with respect to $x$ is $\frac{1}{x}$ .

$2 (x \frac{1}{x} + \ln (x) \frac{d}{d x} [x]) + \frac{d}{d x} [x]$

Step 2.2.4

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$2 (x \frac{1}{x} + \ln (x) \cdot 1) + \frac{d}{d x} [x]$

Step 2.2.5

Combine $x$ and $\frac{1}{x}$ .

$2 (\frac{x}{x} + \ln (x) \cdot 1) + \frac{d}{d x} [x]$

Step 2.2.6

Cancel the common factor of $x$ .

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Step 2.2.6.1

Cancel the common factor.

$2 (\frac{x}{x} + \ln (x) \cdot 1) + \frac{d}{d x} [x]$

Step 2.2.6.2

Rewrite the expression.

$2 (1 + \ln (x) \cdot 1) + \frac{d}{d x} [x]$

Step 2.2.7

Multiply $\ln (x)$ by $1$ .

$2 (1 + \ln (x)) + \frac{d}{d x} [x]$

Step 2.3

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$2 (1 + \ln (x)) + 1$

Step 2.4

Simplify.

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Step 2.4.1

Apply the distributive property.

$2 \cdot 1 + 2 \ln (x) + 1$

Step 2.4.2

Combine terms.

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Step 2.4.2.1

Multiply $2$ by $1$ .

$2 + 2 \ln (x) + 1$

Step 2.4.2.2

Add $2$ and $1$ .

$f'' (x) = 2 \ln (x) + 3$

Step 3

Find the third derivative.

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Step 3.1

By the Sum Rule, the derivative of $2 \ln (x) + 3$ with respect to $x$ is $\frac{d}{d x} [2 \ln (x)] + \frac{d}{d x} [3]$ .

$\frac{d}{d x} [2 \ln (x)] + \frac{d}{d x} [3]$

Step 3.2

Evaluate $\frac{d}{d x} [2 \ln (x)]$ .

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Step 3.2.1

Since $2$ is constant with respect to $x$ , the derivative of $2 \ln (x)$ with respect to $x$ is $2 \frac{d}{d x} [\ln (x)]$ .

$2 \frac{d}{d x} [\ln (x)] + \frac{d}{d x} [3]$

Step 3.2.2

The derivative of $\ln (x)$ with respect to $x$ is $\frac{1}{x}$ .

$2 \frac{1}{x} + \frac{d}{d x} [3]$

Step 3.2.3

Combine $2$ and $\frac{1}{x}$ .

$\frac{2}{x} + \frac{d}{d x} [3]$

Step 3.3

Differentiate using the Constant Rule.

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Step 3.3.1

Since $3$ is constant with respect to $x$ , the derivative of $3$ with respect to $x$ is $0$ .

$\frac{2}{x} + 0$

Step 3.3.2

Add $\frac{2}{x}$ and $0$ .

$f''' (x) = \frac{2}{x}$