Solve by Completing the Square x^2+20x=10

$x^{2} + 20 x = 10$

Step 1

To create a trinomial square on the left side of the equation, find a value that is equal to the square of half of $b$ .

${(\frac{b}{2})}^{2} = {(10)}^{2}$

Step 2

Add the term to each side of the equation.

$x^{2} + 20 x + {(10)}^{2} = 10 + {(10)}^{2}$

Step 3

Simplify the equation.

Simplify the left side.

Raise $10$ to the power of $2$ .

$x^{2} + 20 x + 100 = 10 + {(10)}^{2}$

Simplify the right side.

Simplify $10 + {(10)}^{2}$ .

Raise $10$ to the power of $2$ .

$x^{2} + 20 x + 100 = 10 + 100$

Add $10$ and $100$ .

$x^{2} + 20 x + 100 = 110$

Step 4

Factor the perfect trinomial square into ${(x + 10)}^{2}$ .

${(x + 10)}^{2} = 110$

Step 5

Solve the equation for $x$ .

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x + 10 = \pm \sqrt{110}$

Subtract $10$ from both sides of the equation.

$x = \pm \sqrt{110} - 10$

Step 6

The result can be shown in multiple forms.

Exact Form:

$x = \pm \sqrt{110} - 10$

Decimal Form:

$x = 0.48808848 \dots, - 20.48808848 \dots$