Simplify (3x+9)(3x-9)

$(3 x + 9) (3 x - 9)$

Step 1

Expand $(3 x + 9) (3 x - 9)$ using the FOIL Method.

Apply the distributive property.

$3 x (3 x - 9) + 9 (3 x - 9)$

Apply the distributive property.

$3 x (3 x) + 3 x \cdot - 9 + 9 (3 x - 9)$

Apply the distributive property.

$3 x (3 x) + 3 x \cdot - 9 + 9 (3 x) + 9 \cdot - 9$

Step 2

Simplify and combine like terms.

Simplify each term.

Rewrite using the commutative property of multiplication.

$3 \cdot 3 x \cdot x + 3 x \cdot - 9 + 9 (3 x) + 9 \cdot - 9$

Multiply $x$ by $x$ by adding the exponents.

Move $x$ .

$3 \cdot 3 (x \cdot x) + 3 x \cdot - 9 + 9 (3 x) + 9 \cdot - 9$

Multiply $x$ by $x$ .

$3 \cdot 3 x^{2} + 3 x \cdot - 9 + 9 (3 x) + 9 \cdot - 9$

Multiply $3$ by $3$ .

$9 x^{2} + 3 x \cdot - 9 + 9 (3 x) + 9 \cdot - 9$

Multiply $- 9$ by $3$ .

$9 x^{2} - 27 x + 9 (3 x) + 9 \cdot - 9$

Multiply $3$ by $9$ .

$9 x^{2} - 27 x + 27 x + 9 \cdot - 9$

Multiply $9$ by $- 9$ .

$9 x^{2} - 27 x + 27 x - 81$

Add $- 27 x$ and $27 x$ .

$9 x^{2} + 0 - 81$

Add $9 x^{2}$ and $0$ .

$9 x^{2} - 81$