高次方程的题目,帮个忙
来源:学生作业帮 编辑:搜狗做题网作业帮 分类:数学作业 时间:2024/07/16 20:55:03
高次方程的题目,帮个忙
![](http://img.wesiedu.com/upload/a/af/aaf83a4f790f710deaf0c117d4e5d184.jpg)
![](http://img.wesiedu.com/upload/2/f6/2f6743fcc7bfd793db2ce4af7167fd06.jpg)
5x3-7x2+2=0
4x3+12x2-7x+-30=0
拜托了TUT感激不尽,所有作业都OK了就这两题不会了.
![](http://img.wesiedu.com/upload/a/af/aaf83a4f790f710deaf0c117d4e5d184.jpg)
![](http://img.wesiedu.com/upload/2/f6/2f6743fcc7bfd793db2ce4af7167fd06.jpg)
5x3-7x2+2=0
4x3+12x2-7x+-30=0
拜托了TUT感激不尽,所有作业都OK了就这两题不会了.
![高次方程的题目,帮个忙](/uploads/image/z/8556736-40-6.jpg?t=%E9%AB%98%E6%AC%A1%E6%96%B9%E7%A8%8B%E7%9A%84%E9%A2%98%E7%9B%AE%2C%E5%B8%AE%E4%B8%AA%E5%BF%99)
1.
对5x3-7x2+2=0试1成立.凑x-1
5x^3-5x^2-2x^2+2x-2x+2=0
5x^2(x-1)-2x(x-1)-2(x-1)=0
(x-1)(5x^2-2x-2)=0
x1=1,x2=(1-√11)/5,x3=(1+√11)/5,
2.
对4x3+12x2-7x-30=0试-2成立.凑x+2
4x^3+8x^2+4x^2+8x-15x-30=0
4x^2(x+2)+4x(x+2)-15(x+2)=0
(x+2)(4x^2+4x-15)=0
(x+2)(2x+5)(2x-3)=0
x1=-2,x2=-5/2,x3=3/2
对5x3-7x2+2=0试1成立.凑x-1
5x^3-5x^2-2x^2+2x-2x+2=0
5x^2(x-1)-2x(x-1)-2(x-1)=0
(x-1)(5x^2-2x-2)=0
x1=1,x2=(1-√11)/5,x3=(1+√11)/5,
2.
对4x3+12x2-7x-30=0试-2成立.凑x+2
4x^3+8x^2+4x^2+8x-15x-30=0
4x^2(x+2)+4x(x+2)-15(x+2)=0
(x+2)(4x^2+4x-15)=0
(x+2)(2x+5)(2x-3)=0
x1=-2,x2=-5/2,x3=3/2