解:(1)原式=﹣4×7+3×6+8 =﹣28+18+8 =﹣2; (2)原式=﹣1﹣×24+×24+×24﹣4×3 =﹣1﹣18+4+9﹣12 =﹣18; (3)原式=5abc﹣2a2b﹣[3abc﹣12ab2﹣3a2b] =5abc﹣2a2b﹣3abc+12ab2+3a2b =2abc+a2b+12ab2; (4)原式=﹣x2+x﹣2﹣x+2 =﹣x2﹣x; (5)原式=2x3﹣xyz﹣2x3+2y3﹣2xyz+xyz﹣2y3 =﹣2xyz; (6)原式=2x2+x﹣2[x2﹣6x2+2x] =2x2+x﹣2x2+12x2﹣4x =12x2﹣3x. |