作业帮已知（a＋2）²+丨3b-1丨=0,求3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab的值
来源：学生作业帮助网 编辑：作业帮 时间：2024/04/29 22:30:58
![已知（a＋2）²+丨3b-1丨=0,求3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab的值](/uploads/image/z/3809474-26-4.jpg?t=%E5%B7%B2%E7%9F%A5%EF%BC%88a%EF%BC%8B2%EF%BC%89%26%23178%3B%2B%E4%B8%A83b-1%E4%B8%A8%3D0%2C%E6%B1%823a%26%23178%3Bb-%5B3ab%26%23178%3B-6%EF%BC%88ab-%26%23189%3Ba%26%23178%3Bb%EF%BC%89%2B4ab%5D-2ab%E7%9A%84%E5%80%BC)
已知（a＋2）²+丨3b-1丨=0,求3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab的值
已知（a＋2）²+丨3b-1丨=0,求3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab的值
已知（a＋2）²+丨3b-1丨=0,求3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab的值
∵（a＋2）²+丨3b-1丨=0
∴（a＋2）²≥0,丨3b-1丨≥0
∴a=-2,b=1/3
∵3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab
=3a²b-[3ab²-6ab+3a²b+4ab]-2ab
=3a²b-3ab²+6ab-3a²b-4ab-2ab
=-3ab²
把a=-2,b=1/3代入得
=-3·（-2)·(1/3)²
=2/3
由（a＋2）²+丨3b-1丨=0
有a+2=0,3b-1=0
则a=-2,b=1/3
3a²b-[3ab²-6（ab-½a²b）+4ab]-2ab=3a²b-3ab²+6ab-3a²b-4ab-2ab=-3ab²=-3*(-2)*(1/3)*(1/3)=2/3