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斜率为1的直线l与椭圆x^2/4+y^2=1相交于A,B两点,则AB最大值是多少
人气:241 ℃ 时间:2019-08-18 15:07:07
解答
let A(x1,y1),B(x2,y2)let equation of the line l bey= x+c ( c is a constant) (1)sub (1) into ellipsex^2/4 + (x+c)^2= 15x^2+ 8cx + 4(c^2-1) =0x1+x2 = -8c/5 (3) x1x2= 4(c^2-1)/5 (4)Similarly(y-c)^2/4 + y...
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