近几年中考数学压轴题中,常出现有关二次函数图象上的最值点问题.这类问题有时用切线法解答更简洁.例题(2011年芜湖中考)如图1,平面直角坐标系中,平行四边形ABOC如图放置.点A、C的坐标分别为(0,3)、(-1,0),将此平行四边形绕点O顺时针旋转90°,得到平行四边形A’B’OC’.(1)若抛物线过点C、A、A’,求此抛物线 In recent years, mathematics finale in the middle school entrance examination questions, often appear on the quadratic function of the most value point of the problem .This kind of problem sometimes using tangent method to answer more concise .Example (Wuhu in 2011) as shown in Figure 1, rectangular Cartesian coordinate system , The parallelogram ABOC is placed as shown in Figure 1. The coordinates of the points A and C are (0,3) and (-1,0), respectively, and the parallelogram is rotated clockwise by 90 ° around the point O to obtain a parallelogram A’B ’ OC ’. (1) If the parabola crosses C, A, A’, find the parabola