Solve Using the Quadratic Formula x^2+22x+21=0

$x^{2} + 22 x + 21 = 0$

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 $a = 1$ , $b = 22$ , and $c = 21$ into the quadratic formula and solve for $x$ .

$\frac{- 22 \pm \sqrt{22^{2} - 4 \cdot (1 \cdot 21)}}{2 \cdot 1}$

Step 3

Simplify.

Simplify the numerator.

Raise $22$ to the power of $2$ .

$x = \frac{- 22 \pm \sqrt{484 - 4 \cdot 1 \cdot 21}}{2 \cdot 1}$

Multiply $- 4 \cdot 1 \cdot 21$ .

Multiply $- 4$ by $1$ .

$x = \frac{- 22 \pm \sqrt{484 - 4 \cdot 21}}{2 \cdot 1}$

Multiply $- 4$ by $21$ .

$x = \frac{- 22 \pm \sqrt{484 - 84}}{2 \cdot 1}$

Subtract $84$ from $484$ .

$x = \frac{- 22 \pm \sqrt{400}}{2 \cdot 1}$

Rewrite $400$ as $20^{2}$ .

$x = \frac{- 22 \pm \sqrt{20^{2}}}{2 \cdot 1}$

Pull terms out from under the radical, assuming positive real numbers.

$x = \frac{- 22 \pm 20}{2 \cdot 1}$

Multiply $2$ by $1$ .

$x = \frac{- 22 \pm 20}{2}$

Simplify $\frac{- 22 \pm 20}{2}$ .

$x = - 11 \pm 10$

Step 4

The final answer is the combination of both solutions.

$x = - 1, - 21$