题目

先化简，后求值： ，其中 。 答案：解： (1+1x)⋅xx2−1= (xx+1x)⋅x(x+1)(x−1)= x+1x⋅x(x+1)(x−1)= 1x−1当 x=5+1 时原式= 1x−1 = 15+1−1 = 55 We' ve published large quantities of books. This year___ we've published three million. A. only     B. just      C. alone     D. merely