Find the Axis of Symmetry f(x)=5x^2+10x-2

$f (x) = 5 x^{2} + 10 x - 2$

Step 1

Write $f (x) = 5 x^{2} + 10 x - 2$ as an equation.

$y = 5 x^{2} + 10 x - 2$

Step 2

Rewrite the equation in vertex form.

Complete the square for $5 x^{2} + 10 x - 2$ .

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

$a = 5$

$b = 10$

$c = - 2$

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 $d = \frac{b}{2 a}$ .

$d = \frac{10}{2 \cdot 5}$

Simplify the right side.

Cancel the common factor of $10$ and $2$ .

Factor $2$ out of $10$ .

$d = \frac{2 \cdot 5}{2 \cdot 5}$

Cancel the common factors.

Factor $2$ out of $2 \cdot 5$ .

$d = \frac{2 \cdot 5}{2 (5)}$

Cancel the common factor.

$d = \frac{2 \cdot 5}{2 \cdot 5}$

Rewrite the expression.

$d = \frac{5}{5}$

Cancel the common factor of $5$ .

Cancel the common factor.

$d = \frac{5}{5}$

Rewrite the expression.

$d = 1$

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 $e = c - \frac{b^{2}}{4 a}$ .

$e = - 2 - \frac{10^{2}}{4 \cdot 5}$

Simplify the right side.

Simplify each term.

Raise $10$ to the power of $2$ .

$e = - 2 - \frac{100}{4 \cdot 5}$

Multiply $4$ by $5$ .

$e = - 2 - \frac{100}{20}$

Divide $100$ by $20$ .

$e = - 2 - 1 \cdot 5$

Multiply $- 1$ by $5$ .

$e = - 2 - 5$

Subtract $5$ from $- 2$ .

$e = - 7$

Substitute the values of $a$ , $d$ , and $e$ into the vertex form $5 {(x + 1)}^{2} - 7$ .

$5 {(x + 1)}^{2} - 7$

Set $y$ equal to the new right side.

$y = 5 {(x + 1)}^{2} - 7$

Step 3

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

$a = 5$

$h = - 1$

$k = - 7$

Step 4

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

Opens Up

Step 5

Find the vertex $(h, k)$ .

$(- 1, - 7)$

Step 6

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.

$\frac{1}{4 \cdot 5}$

Multiply $4$ by $5$ .

$\frac{1}{20}$

Step 7

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.

$(- 1, - \frac{139}{20})$

Step 8

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

$x = - 1$

Step 9

Find the Axis of Symmetry f(x)=5x^2+10x-2

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