(-a^2bc)^2乘1/2a(bc)^3-(abc)^3乘(abc)^2
=a^4b²c²×1/2ab³c³-a³b³c³×a²b²c²
=1/2a^5b^5c^5-a^5b^5c^5
=-1/2a^5b^5c^5