数学太太探讨

5august · 发表于 2010-1-15 12:02:23

142 0.00007/700000=

是10的-10次么

偶绕啦

－４５到９９之间能被７整除的数

偶是20吗，有版本是21的，大家确认啊

大荣 · 发表于 2010-1-15 13:51:12

142, 改成科学计算法，0.00007=7*10^(-5), 70000=7*10^5, 指数想减得-10.

第二题，区间(-45,99)中能整除7数最小和最大值分别是，-42=7*(-6), 98=7*(14). 那么-6到14间连续整数都符合，注意是inclusive的。14-(-6)+1=21

5august · 发表于 2010-1-15 14:09:40

不好意思啊，第二题我数了半天就20个啊，
借问下，0不能算吧

大荣 · 发表于 2010-1-15 14:17:37

算0的。

不好意思啊，第二题我数了半天就20个啊，
借问下，0不能算吧

-- by 会员 5august (2010/1/15 14:09:40)

5august · 发表于 2010-1-15 14:37:38

LS确定算0哦，万一偶遇此题我就不管三七二十一写21啦

大荣 · 发表于 2010-1-15 14:46:33

lz太可爱啦。下面是OG里math review的整除定义，仔细读一下。

注意第一段中n只要是整数就行，可以为0.第二段的例子也说明商可以0.所以0=(7)(0),确认0能被7整除。

1. Properties of Integers
An integer is any number in the set {. . . –3, –2, –1, 0, 1, 2, 3, . . .}. If x and y are integers and x ≠ 0,
then x is a divisor (factor) of y provided that y = xn for some integer n. In this case, y is also said to
be divisible by x or to be a multiple of x. For example, 7 is a divisor or factor of 28 since 28 = (7)(4),
but 8 is not a divisor of 28 since there is no integer n such that 28 = 8n.

If x and y are positive integers, there exist unique integers q and r, called the quotient and remainder,
respectively, such that y = xq + r and 0 ≤ r < x. For example, when 28 is divided by 8, the quotient
is 3 and the remainder is 4 since 28 = (8)(3) + 4. Note that y is divisible by x if and only if the
remainder r is 0; for example, 32 has a remainder of 0 when divided by 8 because 32 is divisible
by 8. Also, note that when a smaller integer is divided by a larger integer, the quotient is 0 and the
remainder is the smaller integer. For example, 5 divided by 7 has the quotient 0 and the remainder 5
since 5 = (7)(0) + 5.

数学太太探讨

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