Re: [計量] 幾題數學請教
※ 引述《sead11 (Xavi)》之銘言：
: 1.if x and y are integers and xy+1 is even,
: which of the following must be odd?
: (A)(x^2)(y^2)
: (b)y(x+1)
: (c)x(x+y)
: (d)(x+y)^2
: (e)(x+1)(y+1)
: 答案給的是A
: 但我覺得是D
: 想確定一下答案有沒有問題
答案A沒錯
因為xy+1 is even,所以xy is odd
可再推出 x 與 y 跟別都是奇數
因為兩數相乘若有其中一數為偶數其積必為偶數
得到x&y are odd,再帶回題目就可得解.
PS. D x+y會變成偶數,故不對.
: 2. when n articles are sold for p dollars each,
: the revenue obtained from the sales is $1 more
: than it would be if the price per article were
: $1 higher and one less article were sold.
: which of the following gives n in terms of p?
: (a)n=(p-1)/(p+1)
: (b)n=p+2
: (c)n=p+1
: (d)n=p
: (e)n=p-1
: 這題是我看不懂題目在問什麼
: 想請教一下板上的大家
: 謝謝
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