3a的平方c-【2ab的平方-2(abc-3/2ab的平方)+3a的平方c】-abc
=3a²c-(2ab²-2abc+3ab²+3a²c)-abc
=3a²c-(5ab²-2abc+3a²c)-abc
=3a²c-5ab²+2abc-3a²c-abc
=-5ab²-abc
=-5x(-1/2)x2²-(-1/2)x2x3
=-10+3
=-7