解
(-3x²y)(-4xy²-6x+1)
=12x³y³+18x³y-3x²y
(2a²-1/3a-1/9)(-9a)
=-18a³+3a²+a
3a²(a³b²-2a)-4a(-a²b)²
=3a^5b²-6a³-4a(a^4b²)
=3a^5b²-4a^5b²-6a³
=-a^5b²-6a²