Answer
$6a^4+2a^3$
Work Step by Step
(i) $a^m \cdot a^n = a^{m+n}$
(ii) $x(y+z) = xy + xz$
Use rule (ii) above by distributing $2a^3$ to each term of the binomial to obtain:
$=2a^3(3a) + 2a^3(1)$
Multiply the coefficients together, and then apply rule (i) above to obtain:
$=6a^{3+1} + 2a^3
\\=6a^4+2a^3$
