F.3MATH!help!

2010-08-19 4:10 pm
1.The sides of a triangle have lengths 3 ,6 and n ,where n is an interger .Find all possible values of n.


2.Given a group of numbers:1,x,2,3,5,y,2,1.If the mean of these numbers is 3 and their madian 2.4 , and x<y ,find the values of x and y.

回答 (2)

2010-08-19 5:25 pm
✔ 最佳答案
(1)
3,4,5,6,7,8,9

(2)
(1+x+2+3+5+y+2+1)/8=3
(14+x+y)/8=3
14+x+y=24
x+y=10

有以下情況:
x,y,1,1,2,2,3,5
x,1,1,y,2,2,3,5....1
x,1,1,2,2,y,3,5
x,1,1,2,2,3,y,5
x,1,1,2,2,3,5,y
1,1,x,y,2,2,3,5....1
1,1,x,2,2,y,3,5
1,1,x,2,2,3,y,5
1,1,x,2,2,3,5,y
1,1,2,2,x,y,3,5....1....2
1,1,2,2,x,3,y,5....1....2
1,1,2,2,x,3,5,y....1....2
1,1,2,2,3,x,y,5
1,1,2,2,3,5,x,y
排除第四個數和第五個數都不是x或y(可行的標上1)
標上1後中間的兩個數除了x或y外都是2
即是x或y其中一個是2.8
2<2.8
排除第四個數是x或y(可行的標上2)
摽上2後中間的兩個數都是2和x。
即是x=2.8
x+y=10
y=10-x
x=2.8
y=10-2.8
y=7.2

x=2.8,y=7.2

2010-08-19 09:26:43 補充:
唔明既問我(補充),我會定時check我答咗既題目
參考: ME, ME
2010-08-19 5:09 pm
(1) 3<9.

2010-08-19 09:11:22 補充:
我不是寫3<9,我明明是寫3少於n少於9,為甚麼沒有n?

2010-08-19 09:37:58 補充:
第1題n沒有可能等於3和9,所以001是錯的,正確答案為4, 5, 6, 7, 8.


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