oob73zj92b的部落格

標題:

數 - (51) y ???

發問:

( y ^ 2 - y ) ( y ^ 2 + y ) = y ^ 3 Find y

最佳解答:

• Series
• 隔住手o都八達通@1@
• 請問，邊到有得買q版公仔既杯

 

此文章來自奇摩知識+如有不便請留言告知

( 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

其他解答:

( 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)