a^2b-[2(a^2b-2a^c)-(2b^2c-a^2c)]
=a^2b-2(a^2b-2a^c)+(2b^2c-a^2c)
=a^2b-2a^2b+4a^2c+2b^2c-a^2c
=-a^2b+3a^2c+2b^2c
请参考(2a-b)-(2b-3a)-2(a-2b)的值(2a-b)-(2b-3a)-2(a-2b)的值=2a-b-2b+3a-2a+4b=3a+6b请参考