（1）1/2a^2bc^3•(-2a^2b^2c)^2.
= 1/2a^2bc^3•(4a^4b^4c^2)
=2a^6b^5c^5
(2)-6a•(-1/2a^2-1/3a+2)
=3a^3+2a^2-12a