Simplify (-3a^2b^4)(4a^6n)

$(- 3 a^{2} b^{4}) (4 a^{6} n)$

Multiply $a^{2}$ by $a^{6}$ by adding the exponents.

Move $a^{6}$ .

$- 3 (a^{6} a^{2}) b^{4} (4 n)$

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$- 3 a^{6 + 2} b^{4} (4 n)$

Add $6$ and $2$ .

$- 3 a^{8} b^{4} (4 n)$

Multiply $4$ by $- 3$ .

$- 12 a^{8} b^{4} n$