有些题目看似很难,但在这些题目中其结构特征都隐含着一种组合关系,如果我们能正确利用这种组合关系,便可迅速找到解题的捷径. 1.通项组合 例1 已知函数f(x)=1/(2+4kx)(k∈R)在[1,2]上的最小值为1/18,P1(x1,y1),P2(x2,y2)是函数y=f(x)图象上的两点,且线段P1P2的中点P的横坐标为1/2.若数列{an}的通 Some topics may seem difficult, but in these topics their structural characteristics imply a combinational relationship. If we can correctly use this combination of relationships, we can quickly find the shortest way to solve the problem. 1. General Example 1 The minimum value of the known function f(x) = 1/(2+4kx)(k∈R) on [1,2] is 1/18, P1(x1,y1), P2(x2,y2) are functions Two points on the y=f(x) image, and the abscissa of the midpoint P of the line segment P1P2 is 1/2. If the number column {an}