( 1 + (√5 ) ( 1 - √5 )
(b) Hence, rationalize
2 / 1 + √5
更新1:
其實這樣做更方便 ( 1 + (√5 ) ( 1 - √5 ) = -4 2 / 1 + √5 =2 / 1 + √5 x 1 - √5 / 1 - √5 ............................ 其實大家都做得不錯 交由網友給你們選出答案
F.2 Maths
回答 (3)
2008-04-13 10:21 pm
✔ 最佳答案
a) ( 1 +√5 ) ( 1 - √5 )= (1-(√5)^2)
= (1-5)
= -4
(b) 2 /(1 + √5)
= 2 (1 - √5 )/(1 + √5)( 1 - √5 )
= 2 (1 - √5 )/-4 (by (a))
= (√5 - 1)/2
正常黎講應該咁做
咁做general D
2008-04-13 10:17 pm
(a) ( 1 +√5 ) ( 1 - √5 )
= (1-(√5)^2)
= (1-5)
= -4
因為(A+B)(A-B)=(A^2)-(B^2)
(^2即係二次呀!!!)
(b) 2 /(1 + √5)
= (-4)/ -2(1 + √5)
= ( 1 +√5 ) ( 1 - √5 )/ -2(1 + √5) By (a)
= - ( 1 - √5 )/ 2
= (-1 +√5 )/ 2
簡單
= (1-(√5)^2)
= (1-5)
= -4
因為(A+B)(A-B)=(A^2)-(B^2)
(^2即係二次呀!!!)
(b) 2 /(1 + √5)
= (-4)/ -2(1 + √5)
= ( 1 +√5 ) ( 1 - √5 )/ -2(1 + √5) By (a)
= - ( 1 - √5 )/ 2
= (-1 +√5 )/ 2
簡單
2008-04-13 10:00 pm
(a) ( 1 +√5 ) ( 1 - √5 )
= (1-(√5)^2)
= (1-5)
= -4
因為(A+B)(A-B)=(A^2)-(B^2)
(^2即係二次呀!!!)
(b) 2 /(1 + √5)
= (-4)/ -2(1 + √5)
= ( 1 +√5 ) ( 1 - √5 )/ -2(1 + √5) By (a)
= - ( 1 - √5 )/ 2
= (-1 +√5 )/ 2
= (1-(√5)^2)
= (1-5)
= -4
因為(A+B)(A-B)=(A^2)-(B^2)
(^2即係二次呀!!!)
(b) 2 /(1 + √5)
= (-4)/ -2(1 + √5)
= ( 1 +√5 ) ( 1 - √5 )/ -2(1 + √5) By (a)
= - ( 1 - √5 )/ 2
= (-1 +√5 )/ 2
收錄日期: 2021-04-23 17:54:31
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