2x^2+5xy-3y^2=0(2x - y)(x + 3y) = 0y = 2x 或者x = -3y当y = 2x时(x^2-y^2)/xy = x/y - y/x = 1/2 - 2 = -3/2当x = -3y时(x^2-y^2)/xy = x/y - y/x = -3 + 1/3 = -8/3