概華论与敲理统外「 X 1 2 3 Pi=P(X=x} 1 1 1 1 1 6 9 18 3 1 1 2 a B +a+B 3 12 1 2 P.=P(Y=y) a 8+B +a+B 3 0)由分布律的性质知a≥月≥子+a+月=1 故a与应满足的条件是：a≥0，B≥0且a+B= 1 3(1)由分布律的性质知   0,   0, 1, 3 2 + +  = . 3 1 故与应满足的条件是:  0,   0 且 +  = X Y 1 2 3 1 2 6 1 9 1 18 1 3 1   { } i i p = P X = x • 3 1 + +  3 1 { } j j p = P Y = y • 2 1 + 9 1 +  18 1 + +  3 2