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，...

RaymondoLUO

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.