设A(x1,y1);B(x2,y2)
由y=kx-2和y^2=8x得:(kx-2)^2=8x
化简得:k^2x^2-(4k+8)x+4=0
x1+x2=(4k+8)/(k^2)=4,k=2或-1
因为k=-1时,△=0,A、B重合,故舍去
所以k=2,此时易得x1+x2=4,x1x2=1,y1+y2=4,y1y2=-8
[AB]^2=(x1-x2)^2+(y1-y2)^2=60
AB=2√15
设A(x1,y1);B(x2,y2)
由y=kx-2和y^2=8x得:(kx-2)^2=8x
化简得:k^2x^2-(4k+8)x+4=0
x1+x2=(4k+8)/(k^2)=4,k=2或-1
因为k=-1时,△=0,A、B重合,故舍去
所以k=2,此时易得x1+x2=4,x1x2=1,y1+y2=4,y1y2=-8
[AB]^2=(x1-x2)^2+(y1-y2)^2=60
AB=2√15