Find the Vertex Form f(x)=x^2+11x+28

$f (x) = x^{2} + 11 x + 28$

Step 1

Write $f (x) = x^{2} + 11 x + 28$ as an equation.

$y = x^{2} + 11 x + 28$

Step 2

Complete the square for $x^{2} + 11 x + 28$ .

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

$a = 1$

$b = 11$

$c = 28$

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

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

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

$e = 28 - \frac{11^{2}}{4 \cdot 1}$

Simplify the right side.

Simplify each term.

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

$e = 28 - \frac{121}{4 \cdot 1}$

Multiply $4$ by $1$ .

$e = 28 - \frac{121}{4}$

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

$e = 28 \cdot \frac{4}{4} - \frac{121}{4}$

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

$e = \frac{28 \cdot 4}{4} - \frac{121}{4}$

Combine the numerators over the common denominator.

$e = \frac{28 \cdot 4 - 121}{4}$

Simplify the numerator.

Multiply $28$ by $4$ .

$e = \frac{112 - 121}{4}$

Subtract $121$ from $112$ .

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

Move the negative in front of the fraction.

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

Substitute the values of $a$ , $d$ , and $e$ into the vertex form ${(x + \frac{11}{2})}^{2} - \frac{9}{4}$ .

${(x + \frac{11}{2})}^{2} - \frac{9}{4}$

Step 3

Set $y$ equal to the new right side.

$y = {(x + \frac{11}{2})}^{2} - \frac{9}{4}$