设连续型随机变量X,Y的概率密度函数分别为fx(x),f1(y),且相互-|||-立,若 =X+Y, 则 _(2)(x)= __-|||-A _(x)(x)(f)_(Y)(y)-|||-B _(x)(x)+(f)_(y)(y)+-|||-C (int )_(-infty )^+infty (f)_(x)(x)(f)_(Y)(z-x)dx+-|||-D (int )_(-infty )^+infty [ (f)_(x)(x)+f(y-2)] dx