Precalculus Examples

$x^{2} + 16 x - 2 y + 46 = 0$

Step 1

Rewrite the equation in vertex form.

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Step 1.1

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

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Step 1.1.1

Move all terms not containing $y$ to the right side of the equation.

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Step 1.1.1.1

Subtract $x^{2}$ from both sides of the equation.

$16 x - 2 y + 46 = - x^{2}$

Step 1.1.1.2

Subtract $16 x$ from both sides of the equation.

$- 2 y + 46 = - x^{2} - 16 x$

Step 1.1.1.3

Subtract $46$ from both sides of the equation.

$- 2 y = - x^{2} - 16 x - 46$

Step 1.1.2

Divide each term in $- 2 y = - x^{2} - 16 x - 46$ by $- 2$ and simplify.

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Step 1.1.2.1

Divide each term in $- 2 y = - x^{2} - 16 x - 46$ by $- 2$ .

$\frac{- 2 y}{- 2} = \frac{- x^{2}}{- 2} + \frac{- 16 x}{- 2} + \frac{- 46}{- 2}$

Step 1.1.2.2

Simplify the left side.

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Step 1.1.2.2.1

Cancel the common factor of $- 2$ .

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Step 1.1.2.2.1.1

Cancel the common factor.

$\frac{- 2 y}{- 2} = \frac{- x^{2}}{- 2} + \frac{- 16 x}{- 2} + \frac{- 46}{- 2}$

Step 1.1.2.2.1.2

Divide $y$ by $1$ .

$y = \frac{- x^{2}}{- 2} + \frac{- 16 x}{- 2} + \frac{- 46}{- 2}$

Step 1.1.2.3

Simplify the right side.

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Step 1.1.2.3.1

Simplify each term.

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Step 1.1.2.3.1.1

Dividing two negative values results in a positive value.

$y = \frac{x^{2}}{2} + \frac{- 16 x}{- 2} + \frac{- 46}{- 2}$

Step 1.1.2.3.1.2

Cancel the common factor of $- 16$ and $- 2$ .

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Step 1.1.2.3.1.2.1

Factor $- 2$ out of $- 16 x$ .

$y = \frac{x^{2}}{2} + \frac{- 2 (8 x)}{- 2} + \frac{- 46}{- 2}$

Step 1.1.2.3.1.2.2

Cancel the common factors.

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Step 1.1.2.3.1.2.2.1

Factor $- 2$ out of $- 2$ .

$y = \frac{x^{2}}{2} + \frac{- 2 (8 x)}{- 2 (1)} + \frac{- 46}{- 2}$

Step 1.1.2.3.1.2.2.2

Cancel the common factor.

$y = \frac{x^{2}}{2} + \frac{- 2 (8 x)}{- 2 \cdot 1} + \frac{- 46}{- 2}$

Step 1.1.2.3.1.2.2.3

Rewrite the expression.

$y = \frac{x^{2}}{2} + \frac{8 x}{1} + \frac{- 46}{- 2}$

Step 1.1.2.3.1.2.2.4

Divide $8 x$ by $1$ .

$y = \frac{x^{2}}{2} + 8 x + \frac{- 46}{- 2}$

Step 1.1.2.3.1.3

Divide $- 46$ by $- 2$ .

$y = \frac{x^{2}}{2} + 8 x + 23$

Step 1.2

Complete the square for $\frac{x^{2}}{2} + 8 x + 23$ .

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Step 1.2.1

Use the form $a x^{2} + b x + c$ , to find the values of $a$ , $b$ , and $c$ .

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

$b = 8$

$c = 23$

Step 1.2.2

Consider the vertex form of a parabola.

$a {(x + d)}^{2} + e$

Step 1.2.3

Find the value of $d$ using the formula $d = \frac{b}{2 a}$ .

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Step 1.2.3.1

Substitute the values of $a$ and $b$ into the formula $d = \frac{b}{2 a}$ .

$d = \frac{8}{2 (\frac{1}{2})}$

Step 1.2.3.2

Simplify the right side.

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Step 1.2.3.2.1

Cancel the common factor of $8$ and $2$ .

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Step 1.2.3.2.1.1

Factor $2$ out of $8$ .

$d = \frac{2 \cdot 4}{2 (\frac{1}{2})}$

Step 1.2.3.2.1.2

Cancel the common factors.

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Step 1.2.3.2.1.2.1

Cancel the common factor.

$d = \frac{2 \cdot 4}{2 (\frac{1}{2})}$

Step 1.2.3.2.1.2.2

Rewrite the expression.

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

Step 1.2.3.2.2

Multiply the numerator by the reciprocal of the denominator.

$d = 4 \cdot 2$

Step 1.2.3.2.3

Multiply $4$ by $2$ .

$d = 8$

Step 1.2.4

Find the value of $e$ using the formula $e = c - \frac{b^{2}}{4 a}$ .

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Step 1.2.4.1

Substitute the values of $c$ , $b$ and $a$ into the formula $e = c - \frac{b^{2}}{4 a}$ .

$e = 23 - \frac{8^{2}}{4 (\frac{1}{2})}$

Step 1.2.4.2

Simplify the right side.

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Step 1.2.4.2.1

Simplify each term.

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Step 1.2.4.2.1.1

Raise $8$ to the power of $2$ .

$e = 23 - \frac{64}{4 (\frac{1}{2})}$

Step 1.2.4.2.1.2

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

$e = 23 - \frac{64}{\frac{4}{2}}$

Step 1.2.4.2.1.3

Divide $4$ by $2$ .

$e = 23 - \frac{64}{2}$

Step 1.2.4.2.1.4

Divide $64$ by $2$ .

$e = 23 - 1 \cdot 32$

Step 1.2.4.2.1.5

Multiply $- 1$ by $32$ .

$e = 23 - 32$

Step 1.2.4.2.2

Subtract $32$ from $23$ .

$e = - 9$

Step 1.2.5

Substitute the values of $a$ , $d$ , and $e$ into the vertex form $\frac{1}{2} {(x + 8)}^{2} - 9$ .

$\frac{1}{2} {(x + 8)}^{2} - 9$

Step 1.3

Set $y$ equal to the new right side.

$y = \frac{1}{2} \cdot {(x + 8)}^{2} - 9$

Step 2

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

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

$h = - 8$

$k = - 9$

Step 3

Find the vertex $(h, k)$ .

$(- 8, - 9)$

Step 4