弦|AB|=6
y=2x+b
x^2/3-y^2/2=1
2x^2-3(2x+b)^2=6
10x^2+12bx+6+3b^2=0
xA+xB=-12b/10=-1.2b
xA*xB=0.6+0.3b^2
(xA-xB)^2=(xA+xB)^2-4xA*xB=(-1.2b)^2-4*(0.6+0.3b^2)=0.24b^2-2.4
(xA-xB)^2+(yA-yB)^2=5(xA-xB)^2=5*(0.24b^2-2.4)=AB^2=6^2
b=40
b=土2√10
L:y=2x土2√10