题目20.设随机变量(UND,Y)的联合概率密度为 f(x,y)= ) 0,0lt xlt 1,0lt ylt 2x 0 . 试求:-|||-(1)常数c;-|||-(2)fx(x)和fy((y);-|||-(3)判断X与Y的独立性.题目解答答案