椭圆4x方+9y方=144内有一点P(3,2),过P点的弦恰好以P为中点,求弦长
弦长~我怎么算的数目不对呢~
人气:319 ℃ 时间:2019-10-19 23:49:53
解答
设AB中点为PA(x1,y1)B(x2,y2)4x1²+9y1²=1444x2²+9y2²=144两式相减4(x1²-x2²)+9(y1²-y2²)=04(x1+x2)(x1-x2)+9(y1+y2)(y1-y2)=0根据题意x1+x2=6,y1+y2=4代入,化简(y1-y2)...
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