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下面结合2012年上海中考试题第24题进行分析,并进行变化,探究此类动态三角形构造的一类问题的解法,供参考.图1例(2012上海中考第24题)如图1所示,在平面直角坐标系中,二次函数y=ax2+6x+c的图像经过点A(4,0),B(-1,0),与y轴交于点C,点D在线段OC上,OD=t,点E在第二象限,∠ADE=90°,tan∠DAE=12,EF⊥OD垂足为F,(1)求这个二次函数的解析式;(2)求线段、的长;()当时,求的值
The following combination of 2012 Shanghai senior high school entrance examination questions No. 24 analysis, and changes to explore such a dynamic triangle structure of a class of solution, for reference.Figure 1 (2012 Shanghai senior high school entrance exam questions 24) shown in Figure 1, In the Cartesian coordinate system, the image of the quadratic function y = ax2 + 6x + c passes through points A (4,0), B (-1,0), intersects the y-axis at point C, and point D is on segment OC , OD = t, the point E in the second quadrant, ∠ADE = 90 °, tan ∠ DAE = 12, EF ⊥ O D foot is F, (1) Find the analytic formula of this quadratic function; (2) The length; () At that time, the value of seeking