Find the Vertex y=x^2+3x-28

$y = x^{2} + 3 x - 28$

Step 1

Rewrite the equation in vertex form.

Complete the square for $x^{2} + 3 x - 28$ .

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

$a = 1$

$b = 3$

$c = - 28$

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

$d = \frac{3}{2 \cdot 1}$

Multiply $2$ by $1$ .

$d = \frac{3}{2}$

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

$e = - 28 - \frac{3^{2}}{4 \cdot 1}$

Simplify the right side.

Simplify each term.

Raise $3$ to the power of $2$ .

$e = - 28 - \frac{9}{4 \cdot 1}$

Multiply $4$ by $1$ .

$e = - 28 - \frac{9}{4}$

To write $- 28$ as a fraction with a common denominator, multiply by $\frac{4}{4}$ .

$e = - 28 \cdot \frac{4}{4} - \frac{9}{4}$

Combine $- 28$ and $\frac{4}{4}$ .

$e = \frac{- 28 \cdot 4}{4} - \frac{9}{4}$

Combine the numerators over the common denominator.

$e = \frac{- 28 \cdot 4 - 9}{4}$

Simplify the numerator.

Multiply $- 28$ by $4$ .

$e = \frac{- 112 - 9}{4}$

Subtract $9$ from $- 112$ .

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

Move the negative in front of the fraction.

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

Substitute the values of $a$ , $d$ , and $e$ into the vertex form ${(x + \frac{3}{2})}^{2} - \frac{121}{4}$ .

${(x + \frac{3}{2})}^{2} - \frac{121}{4}$

Set $y$ equal to the new right side.

$y = {(x + \frac{3}{2})}^{2} - \frac{121}{4}$

Step 2

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

$a = 1$

$h = - \frac{3}{2}$

$k = - \frac{121}{4}$

Step 3

Find the vertex $(h, k)$ .

$(- \frac{3}{2}, - \frac{121}{4})$

Step 4

Find the Vertex y=x^2+3x-28

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