※ 引述《chenemily (天天保持好心情)》之銘言：
: Is positive integer n divisible by 3 ?
: (1) n^2/36 is an integer.
: (2) 144/n^2 is an integer.
: 答案A
(1)
36=(2^2)*(3^2)
n^2 is divided by (2^2)*(3^2)
so n is divided by (2^1)*(3^1)
(2)
144=(2^4)*(3^2)
144 is divided by n^2
so n^2 colud be (2^4)*(3^2) or (2^2)*(3^2) or 2^4 or 2^2 or 3^2
then n colud be (2^2)*3 or 2*3 or 2^2 or 2 or 3
: Are positive integers p and q both greater than n ?
: (1) p - q is greater than n .
: (2) q > p
: 答案C
(1)
p-q>n
p>n+q
---> p>n;q?n
(2)
q>p?n
(1)+(2)
p>n
q>p ---> q>n
or
q > p
---> n < p-q < 0
p,q>0 so p>n,q>n
: 請問這2題該怎麼想
: 謝 <(_ _ )>
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※ 編輯: musiclife729 來自: 60.251.147.208 (10/14 21:47)