如图,在平面直角坐标系中,O为坐标原点.A,B两点的坐标分别为A(m,0),B(0,n),且|m-n-3|+ 2n-6 =0,点P从A出发

(1) 二者均大于或等于零，而和为零，二者均为零: m - n - 3 = 0 2n - 6 = 0 n = 3, m = 6 OA = 6, OB = 3 (2) t秒时, PA = t, P(6 - t, 0) △POB的面积S = (1/2)|OP|*OB = 3t/2 0 < 3|6 - t|/2 ≤ 3 0 < |6 - t| ≤ 3 6 < t ≤ 8或4 ≤ t < 6 (3) △OAB的面积S