Algebra Examples

$f (x) = \frac{1}{2} \cdot 5^{- x} - 1$

Step 1

Find the x-intercepts.

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Step 1.1

To find the x-intercept(s), substitute in $0$ for $y$ and solve for $x$ .

$0 = \frac{1}{2} \cdot 5^{- x} - 1$

Step 1.2

Solve the equation.

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Step 1.2.1

Rewrite the equation as $\frac{1}{2} \cdot 5^{- x} - 1 = 0$ .

$\frac{1}{2} \cdot 5^{- x} - 1 = 0$

Step 1.2.2

Combine $\frac{1}{2}$ and $5^{- x}$ .

$\frac{5^{- x}}{2} - 1 = 0$

Step 1.2.3

Add $1$ to both sides of the equation.

$\frac{5^{- x}}{2} = 1$

Step 1.2.4

Multiply both sides by $2$ .

$\frac{5^{- x}}{2} \cdot 2 = 1 \cdot 2$

Step 1.2.5

Simplify.

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Step 1.2.5.1

Simplify the left side.

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Step 1.2.5.1.1

Cancel the common factor of $2$ .

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Step 1.2.5.1.1.1

Cancel the common factor.

$\frac{5^{- x}}{2} \cdot 2 = 1 \cdot 2$

Step 1.2.5.1.1.2

Rewrite the expression.

$5^{- x} = 1 \cdot 2$

Step 1.2.5.2

Simplify the right side.

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Step 1.2.5.2.1

Multiply $2$ by $1$ .

$5^{- x} = 2$

Step 1.2.6

Solve for $x$ .

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Step 1.2.6.1

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

$\ln (5^{- x}) = \ln (2)$

Step 1.2.6.2

Expand $\ln (5^{- x})$ by moving $- x$ outside the logarithm.

$- x \ln (5) = \ln (2)$

Step 1.2.6.3

Divide each term in $- x \ln (5) = \ln (2)$ by $- \ln (5)$ and simplify.

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Step 1.2.6.3.1

Divide each term in $- x \ln (5) = \ln (2)$ by $- \ln (5)$ .

$\frac{- x \ln (5)}{- \ln (5)} = \frac{\ln (2)}{- \ln (5)}$

Step 1.2.6.3.2

Simplify the left side.

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Step 1.2.6.3.2.1

Dividing two negative values results in a positive value.

$\frac{x \ln (5)}{\ln (5)} = \frac{\ln (2)}{- \ln (5)}$

Step 1.2.6.3.2.2

Cancel the common factor of $\ln (5)$ .

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Step 1.2.6.3.2.2.1

Cancel the common factor.

$\frac{x \ln (5)}{\ln (5)} = \frac{\ln (2)}{- \ln (5)}$

Step 1.2.6.3.2.2.2

Divide $x$ by $1$ .

$x = \frac{\ln (2)}{- \ln (5)}$

Step 1.2.6.3.3

Simplify the right side.

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Step 1.2.6.3.3.1

Move the negative in front of the fraction.

$x = - \frac{\ln (2)}{\ln (5)}$

Step 1.3

x-intercept(s) in point form.

x-intercept(s): $(- \frac{\ln (2)}{\ln (5)}, 0)$

Step 2

Find the y-intercepts.

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Step 2.1

To find the y-intercept(s), substitute in $0$ for $x$ and solve for $y$ .

$y = \frac{1}{2} \cdot 5^{- (0)} - 1$

Step 2.2

Simplify $\frac{1}{2} \cdot 5^{- (0)} - 1$ .

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Step 2.2.1

Simplify each term.

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Step 2.2.1.1

Multiply $- 1$ by $0$ .

$y = \frac{1}{2} \cdot 5^{0} - 1$

Step 2.2.1.2

Anything raised to $0$ is $1$ .

$y = \frac{1}{2} \cdot 1 - 1$

Step 2.2.1.3

Multiply $\frac{1}{2}$ by $1$ .

$y = \frac{1}{2} - 1$

Step 2.2.2

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$y = \frac{1}{2} - 1 \cdot \frac{2}{2}$

Step 2.2.3

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

$y = \frac{1}{2} + \frac{- 1 \cdot 2}{2}$

Step 2.2.4

Combine the numerators over the common denominator.

$y = \frac{1 - 1 \cdot 2}{2}$

Step 2.2.5

Simplify the numerator.

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Step 2.2.5.1

Multiply $- 1$ by $2$ .

$y = \frac{1 - 2}{2}$

Step 2.2.5.2

Subtract $2$ from $1$ .

$y = \frac{- 1}{2}$

Step 2.2.6

Move the negative in front of the fraction.

$y = - \frac{1}{2}$

Step 2.3

y-intercept(s) in point form.

y-intercept(s): $(0, - \frac{1}{2})$

Step 3

List the intersections.

x-intercept(s): $(- \frac{\ln (2)}{\ln (5)}, 0)$

y-intercept(s): $(0, - \frac{1}{2})$

Step 4