數學-內分比與外分比

2009-06-28 8:54 am
Q1 如題

請問那是什麼?

請附圖


Q2 a與 b 為10〈x〉的平方-17x-26=0 的兩根
(a-1)(b-1)=

Q3 滿足(26-a)的開根號為整數的正整數a有幾個

回答 (3)

2009-06-28 10:19 am
✔ 最佳答案
The answer is as follows:

圖片參考:http://i320.photobucket.com/albums/nn347/old-master/090628_2.jpg?t=1246126650
2009-06-28 9:30 am
Q1(看不見,沒辦法回答)

Q2利用根與係數,得到ab=-(5/13) ,a+b=17/10

所以(a-1)(b-1)=ab-a-b+1=-(5/13)-17/10+1=-(141/130)

Q因為根號(26-a)為正整數,所以26-a必須為完全平方數,故

26-a=0,1,4,9,16,25所以a=26,25,22,17,10,1共6個
2009-06-28 9:27 am
(1) http://tw.myblog.yahoo.com/jw!vDOreNeYFRnhltvO99uR/photo?pid=146
(2)
10x^2 - 17x - 26 = 0
a+b = 17/10 = 1.7
ab = -26/10 = -2.6
(a-1)(b-1)=ab-a-b+1= - 2.6 - 1.7 + 1 = - 3.3
(3) 26-a = x^2 = 0,1,4,9,16,25
  ==> a = 26, 25, 22, 17, 10, 1 ==> 共 6 個


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