Graph y=x^2+11x+24

$y = x^{2} + 11 x + 24$

Step 1

Find the properties of the given parabola.

Rewrite the equation in vertex form.

Complete the square for $x^{2} + 11 x + 24$ .

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

$a = 1$

$b = 11$

$c = 24$

Consider the vertex form of a parabola.

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

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

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

$d = \frac{11}{2 \cdot 1}$

Multiply $2$ by $1$ .

$d = \frac{11}{2}$

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

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

$e = 24 - \frac{11^{2}}{4 \cdot 1}$

Simplify the right side.

Simplify each term.

Raise $11$ to the power of $2$ .

$e = 24 - \frac{121}{4 \cdot 1}$

Multiply $4$ by $1$ .

$e = 24 - \frac{121}{4}$

To write $24$ as a fraction with a common denominator, multiply by $\frac{4}{4}$ .

$e = 24 \cdot \frac{4}{4} - \frac{121}{4}$

Combine $24$ and $\frac{4}{4}$ .

$e = \frac{24 \cdot 4}{4} - \frac{121}{4}$

Combine the numerators over the common denominator.

$e = \frac{24 \cdot 4 - 121}{4}$

Simplify the numerator.

Multiply $24$ by $4$ .

$e = \frac{96 - 121}{4}$

Subtract $121$ from $96$ .

$e = \frac{- 25}{4}$

Move the negative in front of the fraction.

$e = - \frac{25}{4}$

Substitute the values of $a$ , $d$ , and $e$ into the vertex form ${(x + \frac{11}{2})}^{2} - \frac{25}{4}$ .

${(x + \frac{11}{2})}^{2} - \frac{25}{4}$

Set $y$ equal to the new right side.

$y = {(x + \frac{11}{2})}^{2} - \frac{25}{4}$

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

$a = 1$

$h = - \frac{11}{2}$

$k = - \frac{25}{4}$

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

Opens Up

Find the vertex $(h, k)$ .

$(- \frac{11}{2}, - \frac{25}{4})$

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

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

$\frac{1}{4 a}$

Substitute the value of $a$ into the formula.

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

Cancel the common factor of $1$ .

Cancel the common factor.

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

Rewrite the expression.

$\frac{1}{4}$

Find the focus.

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

$(h, k + p)$

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

$(- \frac{11}{2}, - 6)$

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

$x = - \frac{11}{2}$

Find the directrix.

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.

$y = k - p$

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

$y = - \frac{13}{2}$

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

Direction: Opens Up

Vertex: $(- \frac{11}{2}, - \frac{25}{4})$

Focus: $(- \frac{11}{2}, - 6)$

Axis of Symmetry: $x = - \frac{11}{2}$

Directrix: $y = - \frac{13}{2}$

Direction: Opens Up

Vertex: $(- \frac{11}{2}, - \frac{25}{4})$

Focus: $(- \frac{11}{2}, - 6)$

Axis of Symmetry: $x = - \frac{11}{2}$

Directrix: $y = - \frac{13}{2}$

Step 2

Select a few $x$ values, and plug them into the equation to find the corresponding $y$ values. The $x$ values should be selected around the vertex.

Replace the variable $x$ with $- 7$ in the expression.

$f (- 7) = {(- 7)}^{2} + 11 (- 7) + 24$

Simplify the result.

Simplify each term.

Raise $- 7$ to the power of $2$ .

$f (- 7) = 49 + 11 (- 7) + 24$

Multiply $11$ by $- 7$ .

$f (- 7) = 49 - 77 + 24$

Simplify by adding and subtracting.

Subtract $77$ from $49$ .

$f (- 7) = - 28 + 24$

Add $- 28$ and $24$ .

$f (- 7) = - 4$

The final answer is $- 4$ .

$- 4$

The $y$ value at $x = - 7$ is $- 4$ .

$y = - 4$

Replace the variable $x$ with $- 8$ in the expression.

$f (- 8) = {(- 8)}^{2} + 11 (- 8) + 24$

Simplify the result.

Simplify each term.

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

$f (- 8) = 64 + 11 (- 8) + 24$

Multiply $11$ by $- 8$ .

$f (- 8) = 64 - 88 + 24$

Simplify by adding and subtracting.

Subtract $88$ from $64$ .

$f (- 8) = - 24 + 24$

Add $- 24$ and $24$ .

$f (- 8) = 0$

The final answer is $0$ .

$0$

The $y$ value at $x = - 8$ is $0$ .

$y = 0$

Replace the variable $x$ with $- 5$ in the expression.

$f (- 5) = {(- 5)}^{2} + 11 (- 5) + 24$

Simplify the result.

Simplify each term.

Raise $- 5$ to the power of $2$ .

$f (- 5) = 25 + 11 (- 5) + 24$

Multiply $11$ by $- 5$ .

$f (- 5) = 25 - 55 + 24$

Simplify by adding and subtracting.

Subtract $55$ from $25$ .

$f (- 5) = - 30 + 24$

Add $- 30$ and $24$ .

$f (- 5) = - 6$

The final answer is $- 6$ .

$- 6$

The $y$ value at $x = - 5$ is $- 6$ .

$y = - 6$

Replace the variable $x$ with $- 4$ in the expression.

$f (- 4) = {(- 4)}^{2} + 11 (- 4) + 24$

Simplify the result.

Simplify each term.

Raise $- 4$ to the power of $2$ .

$f (- 4) = 16 + 11 (- 4) + 24$

Multiply $11$ by $- 4$ .

$f (- 4) = 16 - 44 + 24$

Simplify by adding and subtracting.

Subtract $44$ from $16$ .

$f (- 4) = - 28 + 24$

Add $- 28$ and $24$ .

$f (- 4) = - 4$

The final answer is $- 4$ .

$- 4$

The $y$ value at $x = - 4$ is $- 4$ .

$y = - 4$

Graph the parabola using its properties and the selected points.

$\begin{array}{c} x & y \\ - 8 & 0 \\ - 7 & - 4 \\ - \frac{11}{2} & - \frac{25}{4} \\ - 5 & - 6 \\ - 4 & - 4 \end{array}$

Step 3

Graph the parabola using its properties and the selected points.

Direction: Opens Up

Vertex: $(- \frac{11}{2}, - \frac{25}{4})$

Focus: $(- \frac{11}{2}, - 6)$

Axis of Symmetry: $x = - \frac{11}{2}$

Directrix: $y = - \frac{13}{2}$

$\begin{array}{c} x & y \\ - 8 & 0 \\ - 7 & - 4 \\ - \frac{11}{2} & - \frac{25}{4} \\ - 5 & - 6 \\ - 4 & - 4 \end{array}$

Step 4

Graph y=x^2+11x+24

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