Find the Vertex Form y=-4x^2-7x+4

$y = - 4 x^{2} - 7 x + 4$

Step 1

Complete the square for $- 4 x^{2} - 7 x + 4$ .

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

$a = - 4$

$b = - 7$

$c = 4$

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

$d = \frac{- 7}{2 \cdot - 4}$

Simplify the right side.

Multiply $2$ by $- 4$ .

$d = \frac{- 7}{- 8}$

Dividing two negative values results in a positive value.

$d = \frac{7}{8}$

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

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

Simplify the right side.

Simplify each term.

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

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

Multiply $4$ by $- 4$ .

$e = 4 - \frac{49}{- 16}$

Move the negative in front of the fraction.

$e = 4 - - \frac{49}{16}$

Multiply $- - \frac{49}{16}$ .

Multiply $- 1$ by $- 1$ .

$e = 4 + 1 (\frac{49}{16})$

Multiply $\frac{49}{16}$ by $1$ .

$e = 4 + \frac{49}{16}$

To write $4$ as a fraction with a common denominator, multiply by $\frac{16}{16}$ .

$e = 4 \cdot \frac{16}{16} + \frac{49}{16}$

Combine $4$ and $\frac{16}{16}$ .

$e = \frac{4 \cdot 16}{16} + \frac{49}{16}$

Combine the numerators over the common denominator.

$e = \frac{4 \cdot 16 + 49}{16}$

Simplify the numerator.

Multiply $4$ by $16$ .

$e = \frac{64 + 49}{16}$

Add $64$ and $49$ .

$e = \frac{113}{16}$

Substitute the values of $a$ , $d$ , and $e$ into the vertex form $- 4 {(x + \frac{7}{8})}^{2} + \frac{113}{16}$ .

$- 4 {(x + \frac{7}{8})}^{2} + \frac{113}{16}$

Step 2

Set $y$ equal to the new right side.

$y = - 4 {(x + \frac{7}{8})}^{2} + \frac{113}{16}$

Find the Vertex Form y=-4x^2-7x+4

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