已知A=2a+3,B=-4a2+3a-1,C=3a2-4a+4,求4A+{2B-[5A-（3B-2C)+6B]+3C}的

4A+{2B-[5A-（3B-2C)+6B]+3C}
=4A+{[2B-(5A-3B+2C+6B)]+3C}
=4A+2B-5A+3B-2C-6B+3C
=-A-B+C
然后将A、B、C分别代入就行了