Calculus Examples

$\frac{e^{x}}{x}$

Step 1

Find the derivative.

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Step 1.1

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

$\frac{x \frac{d}{d x} [e^{x}] - e^{x} \frac{d}{d x} [x]}{x^{2}}$

Step 1.2

Differentiate using the Exponential Rule which states that $\frac{d}{d x} [a^{x}]$ is $a^{x} \ln (a)$ where $a$ = $e$ .

$\frac{x e^{x} - e^{x} \frac{d}{d x} [x]}{x^{2}}$

Step 1.3

Differentiate using the Power Rule.

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Step 1.3.1

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

$\frac{x e^{x} - e^{x} \cdot 1}{x^{2}}$

Step 1.3.2

Multiply $- 1$ by $1$ .

$\frac{x e^{x} - e^{x}}{x^{2}}$

Step 1.4

Simplify.

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Step 1.4.1

Reorder terms.

$\frac{e^{x} x - e^{x}}{x^{2}}$

Step 1.4.2

Factor $e^{x}$ out of $e^{x} x - e^{x}$ .

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Step 1.4.2.1

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

$\frac{e^{x} (x) - e^{x}}{x^{2}}$

Step 1.4.2.2

Factor $e^{x}$ out of $- e^{x}$ .

$\frac{e^{x} (x) + e^{x} \cdot - 1}{x^{2}}$

Step 1.4.2.3

Factor $e^{x}$ out of $e^{x} (x) + e^{x} \cdot - 1$ .

$\frac{e^{x} (x - 1)}{x^{2}}$

Step 2

Set the derivative equal to $0$ then solve the equation $\frac{e^{x} (x - 1)}{x^{2}} = 0$ .

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Step 2.1

Set the numerator equal to zero.

$e^{x} (x - 1) = 0$

Step 2.2

Solve the equation for $x$ .

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Step 2.2.1

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$e^{x} = 0$

$x - 1 = 0$

Step 2.2.2

Set $e^{x}$ equal to $0$ and solve for $x$ .

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Step 2.2.2.1

Set $e^{x}$ equal to $0$ .

$e^{x} = 0$

Step 2.2.2.2

Solve $e^{x} = 0$ for $x$ .

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Step 2.2.2.2.1

Take the natural logarithm of both sides of the equation to remove the variable from the exponent.

$\ln (e^{x}) = \ln (0)$

Step 2.2.2.2.2

The equation cannot be solved because $\ln (0)$ is undefined.

Undefined

Step 2.2.2.2.3

There is no solution for $e^{x} = 0$

No solution

Step 2.2.3

Set $x - 1$ equal to $0$ and solve for $x$ .

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Step 2.2.3.1

Set $x - 1$ equal to $0$ .

$x - 1 = 0$

Step 2.2.3.2

Add $1$ to both sides of the equation.

$x = 1$

Step 2.2.4

The final solution is all the values that make $e^{x} (x - 1) = 0$ true.

$x = 1$

Step 3

Solve the original function $f (x) = \frac{e^{x}}{x}$ at $x = 1$ .

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Step 3.1

Replace the variable $x$ with $1$ in the expression.

$f (1) = \frac{e^{1}}{1}$

Step 3.2

Simplify the result.

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Step 3.2.1

Divide $e^{1}$ by $1$ .

$f (1) = e$

Step 3.2.2

The final answer is $e$ .

$e$

Step 4

The horizontal tangent line on function $f (x) = \frac{e^{x}}{x}$ is $y = e$ .

$y = e$

Step 5