Let p(Xa, Ya), then k 1 * k2 * k3 = ya 3/Xa (xa 2-4), and point p is the right branch of hyperbola x/4-y= 1 (in the first quadrant), so xa. >: 2, Ya>0 and Ya= 1/2 root number XA 2-4, then XA 2-4 = 4YA 2, so K 1 * K2 * K3 = YA 3/XA (XA 2-4) can be simplified as Ya/4Xa and substituted into YA = 6542. 2, so the minimum value is the root number 3/ 16 (desirable) and the maximum value is 1/8 (undesirable). The value range of k 1.k2.k3 is {root number 3/ 16, 1/8).