已知A=(a+2)(a-2),B=2(6-1/2a²),C=(a-1)²,化简3A+2B-C

题目

已知A=(a+2)(a-2),B=2(6-1/2a²),C=(a-1)²,化简3A+2B-C

答案

解
3A+2B-C
=3(a+2)(a-2)+4(6-1/2a²)-(a-1)²
=3(a²-4)+24-2a²-(a²-2a+1)
=(3a²-2a²-a²)+2a+(-12+24-1)
=2a+11