Algebra Examples

$y = 3 x^{2} - 7 x + 2$

Step 1

Rewrite the equation in vertex form.

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Step 1.1

Complete the square for $3 x^{2} - 7 x + 2$ .

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Step 1.1.1

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

$a = 3$

$b = - 7$

$c = 2$

Step 1.1.2

Consider the vertex form of a parabola.

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

Step 1.1.3

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

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Step 1.1.3.1

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

$d = \frac{- 7}{2 \cdot 3}$

Step 1.1.3.2

Simplify the right side.

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Step 1.1.3.2.1

Multiply $2$ by $3$ .

$d = \frac{- 7}{6}$

Step 1.1.3.2.2

Move the negative in front of the fraction.

$d = - \frac{7}{6}$

Step 1.1.4

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

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Step 1.1.4.1

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

$e = 2 - \frac{{(- 7)}^{2}}{4 \cdot 3}$

Step 1.1.4.2

Simplify the right side.

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Step 1.1.4.2.1

Simplify each term.

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Step 1.1.4.2.1.1

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

$e = 2 - \frac{49}{4 \cdot 3}$

Step 1.1.4.2.1.2

Multiply $4$ by $3$ .

$e = 2 - \frac{49}{12}$

Step 1.1.4.2.2

To write $2$ as a fraction with a common denominator, multiply by $\frac{12}{12}$ .

$e = 2 \cdot \frac{12}{12} - \frac{49}{12}$

Step 1.1.4.2.3

Combine $2$ and $\frac{12}{12}$ .

$e = \frac{2 \cdot 12}{12} - \frac{49}{12}$

Step 1.1.4.2.4

Combine the numerators over the common denominator.

$e = \frac{2 \cdot 12 - 49}{12}$

Step 1.1.4.2.5

Simplify the numerator.

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Step 1.1.4.2.5.1

Multiply $2$ by $12$ .

$e = \frac{24 - 49}{12}$

Step 1.1.4.2.5.2

Subtract $49$ from $24$ .

$e = \frac{- 25}{12}$

Step 1.1.4.2.6

Move the negative in front of the fraction.

$e = - \frac{25}{12}$

Step 1.1.5

Substitute the values of $a$ , $d$ , and $e$ into the vertex form $3 {(x - \frac{7}{6})}^{2} - \frac{25}{12}$ .

$3 {(x - \frac{7}{6})}^{2} - \frac{25}{12}$

Step 1.2

Set $y$ equal to the new right side.

$y = 3 {(x - \frac{7}{6})}^{2} - \frac{25}{12}$

Step 2

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

$a = 3$

$h = \frac{7}{6}$

$k = - \frac{25}{12}$

Step 3

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

Opens Up

Step 4

Find the vertex $(h, k)$ .

$(\frac{7}{6}, - \frac{25}{12})$

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.

$\frac{1}{4 \cdot 3}$

Step 5.3

Multiply $4$ by $3$ .

$\frac{1}{12}$

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.

$(\frac{7}{6}, - 2)$

Step 7

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

$x = \frac{7}{6}$

Step 8