1/5单选题
难度：
1.定义：若抛物线的顶点与x轴的两个交点构成的三角形是直角三角形，则这种抛物线就称为：“美丽抛物线”. 如图，直线l：y=
x+b经过点M（0，
），一组抛物线的顶点B1（1，y1），B2（2，y2），B3（3，y3），…Bn（n，yn）（n为正整数），依次是直线l上的点，这组抛物线与x轴正半轴的交点依次是：A1（x1，0），A2（x2，0），A3（x3，0），…An+1（xn+1，0）（n为正整数）. 若x1=d（0＜d＜1），当d为（ ）时，这组抛物线中存在美丽抛物线. 
x+b经过点M（0，），一组抛物线的顶点B1（1，y1），B2（2，y2），B3（3，y3），…Bn（n，yn）（n为正整数），依次是直线l上的点，这组抛物线与x轴正半轴的交点依次是：A1（x1，0），A2（x2，0），A3（x3，0），…An+1（xn+1，0）（n为正整数）. 若x1=d（0＜d＜1），当d为（ ）时，这组抛物线中存在美丽抛物线. | A |  |
| B |  |
| C |  |
| D |  |
正确答案：Qg==
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
x2的图象如图所示，点A0位于坐标原点，点A1，A2，A3，…，A2008在y轴的正半轴上，点B1，B2，B3，…，B2008在二次函数y＝
，S2=
，…；记W=S1+S2+…+Sn-1，当n越来越大时，你猜想W最接近的常数是（ ）
x2（x＞0）的图象于点P1，P2，P3，…Pn，若记△OA1P1的面积为S1，过点P1作P1B1⊥A2P2于点B1，记△P1B1P2的面积为S2，过点P2作P2B2⊥A3P3于点B2，记△P2B2P3的面积为S3，…依次进行下去，最后记△Pn-1Bn-1Pn（n＞1）的面积为Sn，则Sn=（ ）
