先化简,再求值.(2-a²+4a)-(5a²-a-1),其中a=-2
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/05 20:06:33
![先化简,再求值.(2-a²+4a)-(5a²-a-1),其中a=-2](/uploads/image/z/211533-69-3.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC.%EF%BC%882-a%26%23178%3B%2B4a%EF%BC%89-%EF%BC%885a%26%23178%3B-a-1%EF%BC%89%2C%E5%85%B6%E4%B8%ADa%3D-2)
先化简,再求值.(2-a²+4a)-(5a²-a-1),其中a=-2
先化简,再求值.(2-a²+4a)-(5a²-a-1),其中a=-2
先化简,再求值.(2-a²+4a)-(5a²-a-1),其中a=-2
(2-a²+4a)-(5a²-a-1)
=2-a²+4a-5a²+a+1
=-a²-5a²+4a+a+1+2
=-6a²+5a+3
=-6*(-2)²+5*(-2)+3
=-6*4-10+3
=-24-7
=-31