标题: 数学疑惑，2个解不能是sufficent ? ? 求大神解答,得了，答案不出好像都不好意思睡觉啦，... [打印本页] 作者: RaymondoLUO 时间: 2017-2-21 01:52 标题: 数学疑惑，2个解不能是sufficent ? ? 求大神解答,得了，答案不出好像都不好意思睡觉啦，... What is the value of the integer n?
(1)n(n + 2) = 15
(2) （n+2)^n =125
AStatement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
BStatement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
CBOTH statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
DEACH statement ALONE is sufficient.
EStatements (1) and (2) TOGETHER are NOT sufficient.
回答错误 正确答案：B
(1) n(n + 2) = 15 --> n2+2n−15=0 --> (n+5)(n−3)=0 --> n=−5 or n=3. , the value of n is out , sufficient / or not sufficent ?
难道是因为what is the value of the integer N , is 只能是一个解吗？ 两个解难道不是解吗？ 还是因为英文文法的原因，只能一个解。 （ is ）
(2) (n + 2)^n = 125 --> as n is an integer then (n+2)n=1251=53 (125 can be written as integer^integer only in those two ways), only n=3 works: (2+3)3=53=125. Sufficient.