题目
If [k] denotes the least integer greater than k, is [k] = 0?
(1)
(2) 0 ≤ k
选项
A.Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B.Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C.BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D.EACH statement ALONE is sufficient.
E.Statements (1) and (2) TOGETHER are NOT sufficient.
解析
- “如果[k]表示大于k的最小整数,那么[k]=0吗?”
- **条件(1)**
- 对于不等式\(\vert k +\frac{1}{2}\vert\leq\frac{1}{2}\),可拆分为两个不等式:
- 当\(k+\frac{1}{2}\geq0\)即\(k\geq-\frac{1}{2}\)时,\(k+\frac{1}{2}\leq\frac{1}{2}\),解得\(k\leq0\)。综合可得\(-\frac{1}{2}\leq k\leq0\)。
- 当\(k+\frac{1}{2}<0\)即\(k<-\frac{1}{2}\)时,\(-(k +\frac{1}{2})\leq\frac{1}{2}\),即\(k+\frac{1}{2}\geq-\frac{1}{2}\),解得\(k\geq - 1\)。综合可得\(-1\leq k<-\frac{1}{2}\)。
- 综合两种情况,\(-1\leq k\leq0\)。此时[k]可能为0也可能为1,所以条件(1)不充分。
- **条件(2)**
- 当\(0\leq k\)时,大于k的最小整数[k]一定大于0,即[k]≠0,所以条件(2)单独充分。
综上,答案是B,即Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient。