Solve Using the Quadratic Formula x^2-16x+4=0

$x^{2} - 16 x + 4 = 0$

Step 1

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Step 2

Substitute the values $a = 1$ , $b = - 16$ , and $c = 4$ into the quadratic formula and solve for $x$ .

$\frac{16 \pm \sqrt{{(- 16)}^{2} - 4 \cdot (1 \cdot 4)}}{2 \cdot 1}$

Step 3

Simplify.

Simplify the numerator.

Raise $- 16$ to the power of $2$ .

$x = \frac{16 \pm \sqrt{256 - 4 \cdot 1 \cdot 4}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot 4$ .

Multiply $- 4$ by $1$ .

$x = \frac{16 \pm \sqrt{256 - 4 \cdot 4}}{2 \cdot 1}$

Multiply $- 4$ by $4$ .

$x = \frac{16 \pm \sqrt{256 - 16}}{2 \cdot 1}$

Subtract $16$ from $256$ .

$x = \frac{16 \pm \sqrt{240}}{2 \cdot 1}$

Rewrite $240$ as $4^{2} \cdot 15$ .

Factor $16$ out of $240$ .

$x = \frac{16 \pm \sqrt{16 (15)}}{2 \cdot 1}$

Rewrite $16$ as $4^{2}$ .

$x = \frac{16 \pm \sqrt{4^{2} \cdot 15}}{2 \cdot 1}$

Pull terms out from under the radical.

$x = \frac{16 \pm 4 \sqrt{15}}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{16 \pm 4 \sqrt{15}}{2}$

Simplify $\frac{16 \pm 4 \sqrt{15}}{2}$ .

$x = 8 \pm 2 \sqrt{15}$

Step 4

The result can be shown in multiple forms.

Exact Form:

$x = 8 \pm 2 \sqrt{15}$

Decimal Form:

$x = 15.74596669 \dots, 0.25403330 \dots$