Simplify (9x+4)(9x-4)

$(9 x + 4) (9 x - 4)$

Step 1

Expand $(9 x + 4) (9 x - 4)$ using the FOIL Method.

Apply the distributive property.

$9 x (9 x - 4) + 4 (9 x - 4)$

Apply the distributive property.

$9 x (9 x) + 9 x \cdot - 4 + 4 (9 x - 4)$

Apply the distributive property.

$9 x (9 x) + 9 x \cdot - 4 + 4 (9 x) + 4 \cdot - 4$

Step 2

Simplify terms.

Combine the opposite terms in $9 x (9 x) + 9 x \cdot - 4 + 4 (9 x) + 4 \cdot - 4$ .

Reorder the factors in the terms $9 x \cdot - 4$ and $4 (9 x)$ .

$9 x (9 x) - 4 \cdot 9 x + 4 \cdot 9 x + 4 \cdot - 4$

Add $- 4 \cdot 9 x$ and $4 \cdot 9 x$ .

$9 x (9 x) + 0 + 4 \cdot - 4$

Add $9 x (9 x)$ and $0$ .

$9 x (9 x) + 4 \cdot - 4$

Simplify each term.

Rewrite using the commutative property of multiplication.

$9 \cdot 9 x \cdot x + 4 \cdot - 4$

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

Move $x$ .

$9 \cdot 9 (x \cdot x) + 4 \cdot - 4$

Multiply $x$ by $x$ .

$9 \cdot 9 x^{2} + 4 \cdot - 4$

Multiply $9$ by $9$ .

$81 x^{2} + 4 \cdot - 4$

Multiply $4$ by $- 4$ .

$81 x^{2} - 16$