Calculus Examples

$lim_{x \to 0} \frac{x \cdot 3^{x}}{3^{x} - 1}$

Step 1

Apply L'Hospital's rule.

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Step 1.1

Evaluate the limit of the numerator and the limit of the denominator.

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Step 1.1.1

Take the limit of the numerator and the limit of the denominator.

$\frac{lim_{x \to 0} x \cdot 3^{x}}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.2

Evaluate the limit of the numerator.

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Step 1.1.2.1

Split the limit using the Product of Limits Rule on the limit as $x$ approaches $0$ .

$\frac{lim_{x \to 0} x \cdot lim_{x \to 0} 3^{x}}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.2.2

Move the limit into the exponent.

$\frac{lim_{x \to 0} x \cdot 3^{lim_{x \to 0} x}}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.2.3

Evaluate the limits by plugging in $0$ for all occurrences of $x$ .

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Step 1.1.2.3.1

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{0 \cdot 3^{lim_{x \to 0} x}}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.2.3.2

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{0 \cdot 3^{0}}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.2.4

Simplify the answer.

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Step 1.1.2.4.1

Anything raised to $0$ is $1$ .

$\frac{0 \cdot 1}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.2.4.2

Multiply $0$ by $1$ .

$\frac{0}{lim_{x \to 0} 3^{x} - 1}$

Step 1.1.3

Evaluate the limit of the denominator.

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Step 1.1.3.1

Evaluate the limit.

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Step 1.1.3.1.1

Split the limit using the Sum of Limits Rule on the limit as $x$ approaches $0$ .

$\frac{0}{lim_{x \to 0} 3^{x} - lim_{x \to 0} 1}$

Step 1.1.3.1.2

Move the limit into the exponent.

$\frac{0}{3^{lim_{x \to 0} x} - lim_{x \to 0} 1}$

Step 1.1.3.1.3

Evaluate the limit of $1$ which is constant as $x$ approaches $0$ .

$\frac{0}{3^{lim_{x \to 0} x} - 1 \cdot 1}$

Step 1.1.3.2

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{0}{3^{0} - 1 \cdot 1}$

Step 1.1.3.3

Simplify the answer.

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Step 1.1.3.3.1

Simplify each term.

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Step 1.1.3.3.1.1

Anything raised to $0$ is $1$ .

$\frac{0}{1 - 1 \cdot 1}$

Step 1.1.3.3.1.2

Multiply $- 1$ by $1$ .

$\frac{0}{1 - 1}$

Step 1.1.3.3.2

Subtract $1$ from $1$ .

$\frac{0}{0}$

Step 1.1.3.3.3

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 1.1.3.4

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 1.1.4

The expression contains a division by $0$ . The expression is undefined.

Undefined

$\frac{0}{0}$

Step 1.2

Since $\frac{0}{0}$ is of indeterminate form, apply L'Hospital's Rule. L'Hospital's Rule states that the limit of a quotient of functions is equal to the limit of the quotient of their derivatives.

$lim_{x \to 0} \frac{x \cdot 3^{x}}{3^{x} - 1} = lim_{x \to 0} \frac{\frac{d}{d x} [x \cdot 3^{x}]}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3

Find the derivative of the numerator and denominator.

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Step 1.3.1

Differentiate the numerator and denominator.

$lim_{x \to 0} \frac{\frac{d}{d x} [x \cdot 3^{x}]}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.2

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 $g (x) = 3^{x}$ .

$lim_{x \to 0} \frac{x \frac{d}{d x} [3^{x}] + 3^{x} \frac{d}{d x} [x]}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.3

Differentiate using the Exponential Rule which states that $\frac{d}{d x} [a^{x}]$ is $a^{x} \ln (a)$ where $a$ = $3$ .

$lim_{x \to 0} \frac{x (3^{x} \ln (3)) + 3^{x} \frac{d}{d x} [x]}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.4

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

$lim_{x \to 0} \frac{x (3^{x} \ln (3)) + 3^{x} \cdot 1}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.5

Multiply $3^{x}$ by $1$ .

$lim_{x \to 0} \frac{x (3^{x} \ln (3)) + 3^{x}}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.6

Simplify.

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Step 1.3.6.1

Reorder terms.

$lim_{x \to 0} \frac{3^{x} x \ln (3) + 3^{x}}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.6.2

Reorder factors in $3^{x} x \ln (3) + 3^{x}$ .

$lim_{x \to 0} \frac{x \cdot 3^{x} \ln (3) + 3^{x}}{\frac{d}{d x} [3^{x} - 1]}$

Step 1.3.7

By the Sum Rule, the derivative of $3^{x} - 1$ with respect to $x$ is $\frac{d}{d x} [3^{x}] + \frac{d}{d x} [- 1]$ .

$lim_{x \to 0} \frac{x \cdot 3^{x} \ln (3) + 3^{x}}{\frac{d}{d x} [3^{x}] + \frac{d}{d x} [- 1]}$

Step 1.3.8

Differentiate using the Exponential Rule which states that $\frac{d}{d x} [a^{x}]$ is $a^{x} \ln (a)$ where $a$ = $3$ .

$lim_{x \to 0} \frac{x \cdot 3^{x} \ln (3) + 3^{x}}{3^{x} \ln (3) + \frac{d}{d x} [- 1]}$

Step 1.3.9

Since $- 1$ is constant with respect to $x$ , the derivative of $- 1$ with respect to $x$ is $0$ .

$lim_{x \to 0} \frac{x \cdot 3^{x} \ln (3) + 3^{x}}{3^{x} \ln (3) + 0}$

Step 1.3.10

Add $3^{x} \ln (3)$ and $0$ .

$lim_{x \to 0} \frac{x \cdot 3^{x} \ln (3) + 3^{x}}{3^{x} \ln (3)}$

Step 2

Evaluate the limit.

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Step 2.1

Move the term $\frac{1}{\ln (3)}$ outside of the limit because it is constant with respect to $x$ .

$\frac{1}{\ln (3)} lim_{x \to 0} \frac{x \cdot 3^{x} \ln (3) + 3^{x}}{3^{x}}$

Step 2.2

Split the limit using the Limits Quotient Rule on the limit as $x$ approaches $0$ .

$\frac{1}{\ln (3)} \cdot \frac{lim_{x \to 0} x \cdot 3^{x} \ln (3) + 3^{x}}{lim_{x \to 0} 3^{x}}$

Step 2.3

Split the limit using the Sum of Limits Rule on the limit as $x$ approaches $0$ .

$\frac{1}{\ln (3)} \cdot \frac{lim_{x \to 0} x \cdot 3^{x} \ln (3) + lim_{x \to 0} 3^{x}}{lim_{x \to 0} 3^{x}}$

Step 2.4

Move the term $\ln (3)$ outside of the limit because it is constant with respect to $x$ .

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) lim_{x \to 0} x \cdot 3^{x} + lim_{x \to 0} 3^{x}}{lim_{x \to 0} 3^{x}}$

Step 2.5

Split the limit using the Product of Limits Rule on the limit as $x$ approaches $0$ .

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) lim_{x \to 0} x \cdot lim_{x \to 0} 3^{x} + lim_{x \to 0} 3^{x}}{lim_{x \to 0} 3^{x}}$

Step 2.6

Move the limit into the exponent.

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) lim_{x \to 0} x \cdot 3^{lim_{x \to 0} x} + lim_{x \to 0} 3^{x}}{lim_{x \to 0} 3^{x}}$

Step 2.7

Move the limit into the exponent.

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) lim_{x \to 0} x \cdot 3^{lim_{x \to 0} x} + 3^{lim_{x \to 0} x}}{lim_{x \to 0} 3^{x}}$

Step 2.8

Move the limit into the exponent.

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) lim_{x \to 0} x \cdot 3^{lim_{x \to 0} x} + 3^{lim_{x \to 0} x}}{3^{lim_{x \to 0} x}}$

Step 3

Evaluate the limits by plugging in $0$ for all occurrences of $x$ .

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Step 3.1

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) \cdot 0 \cdot 3^{lim_{x \to 0} x} + 3^{lim_{x \to 0} x}}{3^{lim_{x \to 0} x}}$

Step 3.2

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) \cdot 0 \cdot 3^{0} + 3^{lim_{x \to 0} x}}{3^{lim_{x \to 0} x}}$

Step 3.3

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) \cdot 0 \cdot 3^{0} + 3^{0}}{3^{lim_{x \to 0} x}}$

Step 3.4

Evaluate the limit of $x$ by plugging in $0$ for $x$ .

$\frac{1}{\ln (3)} \cdot \frac{\ln (3) \cdot 0 \cdot 3^{0} + 3^{0}}{3^{0}}$

Step 4

Simplify the answer.

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Step 4.1

Simplify the numerator.

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Step 4.1.1

Multiply $\ln (3)$ by $0$ .

$\frac{1}{\ln (3)} \cdot \frac{0 \cdot 3^{0} + 3^{0}}{3^{0}}$

Step 4.1.2

Anything raised to $0$ is $1$ .

$\frac{1}{\ln (3)} \cdot \frac{0 \cdot 1 + 3^{0}}{3^{0}}$

Step 4.1.3

Multiply $0$ by $1$ .

$\frac{1}{\ln (3)} \cdot \frac{0 + 3^{0}}{3^{0}}$

Step 4.1.4

Anything raised to $0$ is $1$ .

$\frac{1}{\ln (3)} \cdot \frac{0 + 1}{3^{0}}$

Step 4.1.5

Add $0$ and $1$ .

$\frac{1}{\ln (3)} \cdot \frac{1}{3^{0}}$

Step 4.2

Anything raised to $0$ is $1$ .

$\frac{1}{\ln (3)} \cdot \frac{1}{1}$

Step 4.3

Cancel the common factor of $1$ .

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Step 4.3.1

Cancel the common factor.

$\frac{1}{\ln (3)} \cdot \frac{1}{1}$

Step 4.3.2

Rewrite the expression.

$\frac{1}{\ln (3)} \cdot 1$

Step 4.4

Multiply $\frac{1}{\ln (3)}$ by $1$ .

$\frac{1}{\ln (3)}$

Step 5

The result can be shown in multiple forms.

Exact Form:

$\frac{1}{\ln (3)}$

Decimal Form:

$0.91023922 \dots$