NN们帮忙看两道Prep的题

IF $1000 is deposited in a bank account and remains in the account along with accumulated interest, the dollar amount of interest, I = 1000* ((1+r/100)^n-1), where r percent is the annual interest rate paid by the bank. Is the annual interest rate paid by the bank greater than 8 percent?

(1) the deposit earns a total of $210 in interest in the first two years.

(2) (1+r/100)^2 > 1.15

答案是A

我不明白的是(2)不是明明可以算出来吗.为什么答案不可以.

2. For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100) + 1, then p is

A between 2 and 10

B between 10 and 20

...

E greater than 40

答案是E,

不太明白怎么做,花了好几分钟.

谢谢!

我来试试吧

第一个题 2算出来R>7点几 无法证明R>8

第二题 2*4*6*....*100+1 前一项的PRIME FACTOR有3,5,7....41,43,47 因为加上1 所以这个PRIME FACTOR应该大于47

# h(100)的prime factor为从2，3，5，7，11，。。到47。

所以h(100)+1必然不能被2,3,....47之中任意一个prime整除

所以h(100)+1的smallest prime factor必然大于47         所以选 E

2 = #336 at http://forum.chasedream.com/dispbbs.asp?BoardID=22&replyID=1609121&id=171137&skin=0

谢谢楼上的解答,我太土了

1题当成等号了,没有算,以为一定能算出来,所以可以判断大小.