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巧设弦中点,妙用作差法,破解弦问题弦中点取决于弦两端点的坐标和,弦斜率取决于弦两端点的坐标差,这对两端点坐标的孪生兄弟,互帮互助,它们的直接关系孕育在设点代入、作差之中.在解决有关弦斜率、隐含弦中点的问题时,若巧设弦中点,妙用作差法,以弦中点坐标作辅助元,则往往可简捷获解.一、给出弦的斜率情况例1斜率为1的直线l与双曲线3x2-y2=1相交于不同的两点A,B,若A,B两点到直线4x-y-1=0的距离
Consistently set the middle point of the string, magical use as the difference method, to solve the string problem String midpoint depends on the coordinates of the two ends of the string, the string slope depends on the coordinates of the two ends of the string difference, which coordinates the two ends of the twin brothers, The direct relationship between them conceived in the set into the place into the poor in. In the solution to the problem of string slope, the hidden point of the string, if the clever set chord midpoint, magic for the difference method, to string coordinates for the auxiliary , You can often get a simple solution. First, give the slope of the string case 1 slope of 1 straight line l and hyperbolic 3x2-y2 = 1 intersect at two different points A, B, if A, B two points to a straight line 4x-y-1 = 0 distance