( y ^ 2 - y ) ( y ^ 2 + y ) = y ^ 3
Find y
數 - (51) y ???
2010-08-02 4:26 am
回答 (2)
2010-08-02 4:54 am
✔ 最佳答案
( y ^ 2 - y ) ( y ^ 2 + y ) = y ^ 3 y^4+y^3-y^3-y^2=y^3
y^4-y^2=y^3
y^2(y^2-1)=y^3
y^2-1=y
y^2-y-1=0
By Quadratic Formula,
y= {- (-1)±√[ (-1)^2-4(1)(-1)]}/2(1)
y=(1+√5)/2 OR 1-√5)/2
y=1.618033989 OR -0.618033988
2010-08-02 5:06 am
( y ^ 2 - y ) ( y ^ 2 + y ) = y ^ 3
y^4+y^3-y^3-y^2=y^3
y^4-y^2=y^3
y^2(y^2-1)=y^3
y^2(y^2-1)-y^3=0
y^2((y^2-1)-y)=0
y=0(repeated) or y^2-y-1=0
y= {- (-1)±√[ (-1)^2-4(1)(-1)]}/2(1) or 0(repeated)
y=(1+√5)/2 OR 1-√5)/2 or 0(repeated)
y=1.618033989 OR -0.618033988 or 0(repeated)
y^4+y^3-y^3-y^2=y^3
y^4-y^2=y^3
y^2(y^2-1)=y^3
y^2(y^2-1)-y^3=0
y^2((y^2-1)-y)=0
y=0(repeated) or y^2-y-1=0
y= {- (-1)±√[ (-1)^2-4(1)(-1)]}/2(1) or 0(repeated)
y=(1+√5)/2 OR 1-√5)/2 or 0(repeated)
y=1.618033989 OR -0.618033988 or 0(repeated)
參考: me
收錄日期: 2021-04-24 09:34:37
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100801000051KK01362