Simplify (3a)^2(7b)^4

${(3 a)}^{2} {(7 b)}^{4}$

Apply the product rule to $3 a$ .

$3^{2} a^{2} {(7 b)}^{4}$

Raise $3$ to the power of $2$ .

$9 a^{2} {(7 b)}^{4}$

Apply the product rule to $7 b$ .

$9 a^{2} (7^{4} b^{4})$

Rewrite using the commutative property of multiplication.

$9 \cdot 7^{4} a^{2} b^{4}$

Raise $7$ to the power of $4$ .

$9 \cdot 2401 a^{2} b^{4}$

Multiply $9$ by $2401$ .

$21609 a^{2} b^{4}$