解:原式=5a-(a²+5a²-3a-6a²+6a)
=5a-6a²+3a+6a²-6a
=5a-3a
=2a
当a=-1/2时,原式=2×(-1/2)=-1
如果是计算结果的话,这种题目一定要先化简,再带入求值。
化简:原式=5a-(a²+5a²-3a-6a²+6a)
=5a-3a
=2a
现在把a=-1/2带入得到 2x(-1/2)=-1
5a-[a²+(5a²-3a)-6(a²-a)]
=5a-(a²+5a²-3a-6a²+6a)
=5a-3a
=2a
=2×(-1/2)
=-1
不懂可追问,有帮助请采纳,谢谢!
5a-(a²+5a²-3a-6a²+6a)=5a-3a=2a=-1
5a-[a²+(5a²-3a)-6(a²-a)]
=5a-(a²+5a²-3a-6a²+6a)
=5a-3a
=2a
=2x(-1/2)
=-1