Trigonometry Examples

$x^{2} - 18 x + 81 = 0$

Step 1

Factor using the perfect square rule.

Tap for more steps...

Step 1.1

Rewrite $81$ as $9^{2}$ .

$x^{2} - 18 x + 9^{2} = 0$

Step 1.2

Check that the middle term is two times the product of the numbers being squared in the first term and third term.

$18 x = 2 \cdot x \cdot 9$

Step 1.3

Rewrite the polynomial.

$x^{2} - 2 \cdot x \cdot 9 + 9^{2} = 0$

Step 1.4

Factor using the perfect square trinomial rule $a^{2} - 2 a b + b^{2} = {(a - b)}^{2}$ , where $a = x$ and $b = 9$ .

${(x - 9)}^{2} = 0$

Step 2

Set the $x - 9$ equal to $0$ .

$x - 9 = 0$

Step 3

Add $9$ to both sides of the equation.

$x = 9$

Step 4

The domain is the set of all valid $x$ values.

${x | x = 9}$

Step 5