Simplify (5r+4)(5r-4)

$(5 r + 4) (5 r - 4)$

Step 1

Expand $(5 r + 4) (5 r - 4)$ using the FOIL Method.

Apply the distributive property.

$5 r (5 r - 4) + 4 (5 r - 4)$

Apply the distributive property.

$5 r (5 r) + 5 r \cdot - 4 + 4 (5 r - 4)$

Apply the distributive property.

$5 r (5 r) + 5 r \cdot - 4 + 4 (5 r) + 4 \cdot - 4$

Step 2

Simplify terms.

Combine the opposite terms in $5 r (5 r) + 5 r \cdot - 4 + 4 (5 r) + 4 \cdot - 4$ .

Reorder the factors in the terms $5 r \cdot - 4$ and $4 (5 r)$ .

$5 r (5 r) - 4 \cdot 5 r + 4 \cdot 5 r + 4 \cdot - 4$

Add $- 4 \cdot 5 r$ and $4 \cdot 5 r$ .

$5 r (5 r) + 0 + 4 \cdot - 4$

Add $5 r (5 r)$ and $0$ .

$5 r (5 r) + 4 \cdot - 4$

Simplify each term.

Rewrite using the commutative property of multiplication.

$5 \cdot 5 r \cdot r + 4 \cdot - 4$

Multiply $r$ by $r$ by adding the exponents.

Move $r$ .

$5 \cdot 5 (r \cdot r) + 4 \cdot - 4$

Multiply $r$ by $r$ .

$5 \cdot 5 r^{2} + 4 \cdot - 4$

Multiply $5$ by $5$ .

$25 r^{2} + 4 \cdot - 4$

Multiply $4$ by $- 4$ .

$25 r^{2} - 16$