因为A点在y=-2/x上所以设A（x,-2/x）又AB//x则B点纵坐标等于A点纵坐标,即yB=-2/x将yB=-2/x带入直线y=x得：xB=-2/x则B（-2/x,-2/x)所以AB^2=(x+2/x)^2,OA=x^2+(2/x)^2即AB^2-OA^2=(x+2/x)^2-x^2-(2/x)^2=x^2+4+(2/x)^...