f5數學題一問?
2011-08-28 4:51 am
given r is root of equation x^2-3x-5=0,find value of r^5-3r^4-5r^3+2r^2-6r
回答 (1)
2011-08-28 5:41 am
✔ 最佳答案
r is a root of the equation x^2-3x-5=0When x=r
r^2-3r-5=0
r^5-3r^4-5r^3+2r^2-6r
=(r^2-3r-5)r^3+2r^2-6r
=0Xr^3+2r^2-6r
=2r^2-6r
=2r^2-6r-10+10
=2(r^2-3r-5)+10
=2X0+10
=10
收錄日期: 2021-04-23 20:43:57
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110827000051KK01082