导数的出现丰富了我们研究函数的手段,同时也改变了我们的思维习惯。曲线在某点处切线的斜率、函数单调性、函数极(最)值、函数零点的个数等问题,都可以转化为对导函数值的分析,而这些问题往往最终又可以转化为对二次方程根的讨论。例1(2011年全国卷文科21) The advent of derivatives has enriched our means of studying functions and has changed our habits of thinking. The slope of the tangent at the point of the curve, the monotonicity of the function, the pole (the most) value of the function, the number of the zero point of the function, etc. can all be transformed into the analysis of the value of the conduction function, and these problems can eventually be transformed into two Sub-root equation discussion. Example 1 (2011 National Literature 21)