(1)设样本X1,X2,···,X6来自总体N(0,1), =(({X)_(1)+(X)_(2)+(X)_(3))}^2-|||-+(({X)_(4)+(X)_(5)+(X)_(6))}^2, 试确定常数C使CY服从x ^2分布.-|||-(2)设样本X1,X2,···X5来自总体N(0,1), =dfrac (C({X)_(1)+(X)_(2))}({({{X)_(3)}^2+({X)_(4)}^2+({X)_(5)}^2)}^1/2} 试确-|||-定常数C使Y服从t分布:-|||-(3)已知 backsim t(n), 求证 ^2approx F(1,n).