(1) used for advertising 丄 OB, OB=OA Because of the regular triangle AOB, OD= 1/2OB Because of B (2 2,0), OA=2, OD= 1, so AD= root (ob = the square of OA-the square of OD) = 3) Let OA be y=kx because A is on the straight line OA, so k= 3 is under the root, so y= 3x(2 is under the root) (2) Because the square of parabola y=ax +bx passes through points A and C, a+b= 3 and 16a+4b=0 under the root are simultaneous, and the solution is a=- 3 under the root.