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
问题描述：
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
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...