b = 1,c^2 = 1/2 a^2,a^2 - b^2 = c^2 = 1/2 a^2,a^2 = 2b^2,a = 根号（2）x^2 / 2 + y^2 = 1x^2 / 2 + (kx-1/3)^2 = 1A(x1,y1),B(x2,y2)(x1-x2)^2 + (y1-y2)^2 = (4根号（26）/9）^2k = +/-1能有详细化简步骤么(1/2 + k^2) x^2 -2k/3 x - 8/9 = 0x1,x2 = (2k/3 +/- 根号（4k^2/9 + 16/9 (2k^2+1)))/(2k^2+1）y1,y2 = kx1 - 1/3, kx2 - 1/3(x1-x2)^2 + (y1-y2)^2 =( k^2+1) (4k^2 / 9 + 16/9 (2k^2+1))/(k^2+1/2)^2 = 16*26/81k^2 = 1