函数f(x)=a*x^3+x+1有极值的充要条件是?a<0先是求导得:f'(x)=3a*x^2+1 然后要有极值就必须满足:b^2-4ac>0,也就是与X轴有2个交点.我想问的是:与X轴有一个交点为什么不行啊?
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/11 09:13:40
![函数f(x)=a*x^3+x+1有极值的充要条件是?a<0先是求导得:f'(x)=3a*x^2+1 然后要有极值就必须满足:b^2-4ac>0,也就是与X轴有2个交点.我想问的是:与X轴有一个交点为什么不行啊?](/uploads/image/z/10371352-40-2.jpg?t=%E5%87%BD%E6%95%B0f%28x%29%3Da%2Ax%5E3%2Bx%2B1%E6%9C%89%E6%9E%81%E5%80%BC%E7%9A%84%E5%85%85%E8%A6%81%E6%9D%A1%E4%BB%B6%E6%98%AF%3Fa%EF%BC%9C0%E5%85%88%E6%98%AF%E6%B1%82%E5%AF%BC%E5%BE%97%EF%BC%9Af%27%28x%29%3D3a%2Ax%5E2%2B1+%E7%84%B6%E5%90%8E%E8%A6%81%E6%9C%89%E6%9E%81%E5%80%BC%E5%B0%B1%E5%BF%85%E9%A1%BB%E6%BB%A1%E8%B6%B3%EF%BC%9Ab%5E2-4ac%EF%BC%9E0%2C%E4%B9%9F%E5%B0%B1%E6%98%AF%E4%B8%8EX%E8%BD%B4%E6%9C%892%E4%B8%AA%E4%BA%A4%E7%82%B9.%E6%88%91%E6%83%B3%E9%97%AE%E7%9A%84%E6%98%AF%EF%BC%9A%E4%B8%8EX%E8%BD%B4%E6%9C%89%E4%B8%80%E4%B8%AA%E4%BA%A4%E7%82%B9%E4%B8%BA%E4%BB%80%E4%B9%88%E4%B8%8D%E8%A1%8C%E5%95%8A%3F)
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