Precalculus Examples

${(x - 4)}^{2} = 2 (y - \frac{5}{2})$

Step 1

Isolate $y$ to the left side of the equation.

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Step 1.1

Rewrite the equation as $2 (y - \frac{5}{2}) = {(x - 4)}^{2}$ .

$2 (y - \frac{5}{2}) = {(x - 4)}^{2}$

Step 1.2

Simplify $2 (y - \frac{5}{2})$ .

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Step 1.2.1

Apply the distributive property.

$2 y + 2 (- \frac{5}{2}) = {(x - 4)}^{2}$

Step 1.2.2

Cancel the common factor of $2$ .

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Step 1.2.2.1

Move the leading negative in $- \frac{5}{2}$ into the numerator.

$2 y + 2 (\frac{- 5}{2}) = {(x - 4)}^{2}$

Step 1.2.2.2

Cancel the common factor.

$2 y + 2 (\frac{- 5}{2}) = {(x - 4)}^{2}$

Step 1.2.2.3

Rewrite the expression.

$2 y - 5 = {(x - 4)}^{2}$

Step 1.3

Add $5$ to both sides of the equation.

$2 y = {(x - 4)}^{2} + 5$

Step 1.4

Divide each term in $2 y = {(x - 4)}^{2} + 5$ by $2$ and simplify.

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Step 1.4.1

Divide each term in $2 y = {(x - 4)}^{2} + 5$ by $2$ .

$\frac{2 y}{2} = \frac{{(x - 4)}^{2}}{2} + \frac{5}{2}$

Step 1.4.2

Simplify the left side.

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Step 1.4.2.1

Cancel the common factor of $2$ .

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Step 1.4.2.1.1

Cancel the common factor.

$\frac{2 y}{2} = \frac{{(x - 4)}^{2}}{2} + \frac{5}{2}$

Step 1.4.2.1.2

Divide $y$ by $1$ .

$y = \frac{{(x - 4)}^{2}}{2} + \frac{5}{2}$

Step 1.5

Reorder terms.

$y = \frac{1}{2} \cdot {(x - 4)}^{2} + \frac{5}{2}$

Step 2

Use the vertex form, $y = a {(x - h)}^{2} + k$ , to determine the values of $a$ , $h$ , and $k$ .

$a = \frac{1}{2}$

$h = 4$

$k = \frac{5}{2}$

Step 3

Since the value of $a$ is positive, the parabola opens up.

Opens Up

Step 4

Find the vertex $(h, k)$ .

$(4, \frac{5}{2})$

Step 5

Find $p$ , the distance from the vertex to the focus.

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Step 5.1

Find the distance from the vertex to a focus of the parabola by using the following formula.

$\frac{1}{4 a}$

Step 5.2

Substitute the value of $a$ into the formula.

$\frac{1}{4 \cdot \frac{1}{2}}$

Step 5.3

Simplify.

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Step 5.3.1

Combine $4$ and $\frac{1}{2}$ .

$\frac{1}{\frac{4}{2}}$

Step 5.3.2

Divide $4$ by $2$ .

$\frac{1}{2}$

Step 6

Find the focus.

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Step 6.1

The focus of a parabola can be found by adding $p$ to the y-coordinate $k$ if the parabola opens up or down.

$(h, k + p)$

Step 6.2

Substitute the known values of $h$ , $p$ , and $k$ into the formula and simplify.

$(4, 3)$

Step 7

Find the axis of symmetry by finding the line that passes through the vertex and the focus.

$x = 4$

Step 8

Find the directrix.

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Step 8.1

The directrix of a parabola is the horizontal line found by subtracting $p$ from the y-coordinate $k$ of the vertex if the parabola opens up or down.

$y = k - p$

Step 8.2

Substitute the known values of $p$ and $k$ into the formula and simplify.

$y = 2$

Step 9

Use the properties of the parabola to analyze and graph the parabola.

Direction: Opens Up

Vertex: $(4, \frac{5}{2})$

Focus: $(4, 3)$

Axis of Symmetry: $x = 4$

Directrix: $y = 2$

Step 10