中四數學題
回答 (2)
2007-01-11 8:01 am
✔ 最佳答案
x的5次方-8x的3次方-9x=x^5-8x^3-9x
=x(x^4-8x^2-9)
=x(x^2-9)(x^2+1)
=x(x+3)(x-3)(x^2+1)
2007-01-11 8:10 am
x^5-8x^3-9x=0
x(x^4-8x^2-9)=0
=>x=0
x^4-8x^2-9=0
(x^2-9)(x^2+1)=0
=>x^2=9
=x=3, x=-3
i don't remember do you have complex number, if no just reject (x^2=-1),
if yes x^(2)=-1, x=i, x=-i
i.e. The roots are x=0, 3, -3, i, -i.
x(x^4-8x^2-9)=0
=>x=0
x^4-8x^2-9=0
(x^2-9)(x^2+1)=0
=>x^2=9
=x=3, x=-3
i don't remember do you have complex number, if no just reject (x^2=-1),
if yes x^(2)=-1, x=i, x=-i
i.e. The roots are x=0, 3, -3, i, -i.
收錄日期: 2021-04-25 16:51:17
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070110000051KK05056