Simplify (a+9)(a-9)

$(a + 9) (a - 9)$

Step 1

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

Apply the distributive property.

$a (a - 9) + 9 (a - 9)$

Apply the distributive property.

$a \cdot a + a \cdot - 9 + 9 (a - 9)$

Apply the distributive property.

$a \cdot a + a \cdot - 9 + 9 a + 9 \cdot - 9$

Step 2

Simplify terms.

Combine the opposite terms in $a \cdot a + a \cdot - 9 + 9 a + 9 \cdot - 9$ .

Reorder the factors in the terms $a \cdot - 9$ and $9 a$ .

$a \cdot a - 9 a + 9 a + 9 \cdot - 9$

Add $- 9 a$ and $9 a$ .

$a \cdot a + 0 + 9 \cdot - 9$

Add $a \cdot a$ and $0$ .

$a \cdot a + 9 \cdot - 9$

Simplify each term.

Multiply $a$ by $a$ .

$a^{2} + 9 \cdot - 9$

Multiply $9$ by $- 9$ .

$a^{2} - 81$