题目

已知，若f(x)=・+1，求：    （1）f(x)的表达式及周期    （2）y=lg[f(x)]的单调递增区间. 答案：解：（1） 周期    （2）由— Who has broken the window in my room?  — Who else ________ it but your naughty boy?    [     ]A. could do       B. could have done    C. might do      D. must have done