求指导本题解题过程，谢谢您！12.设总体x_wo4)xx···X是来自X的简单随机样本.-|||-(1) =a({x)_(1)}^2+b(({x)_(2)+(x)_(3))}^2+c(({x)_(4)-(x)_(5))}^2 试确定常数a,b,c的值,使Y服从卡方分布并确定-|||-自由度;-|||-(2) =dfrac (alpha ({X)_(1)+(X)_(2))}(sqrt {{{X)_(3)}^2+({X)_(4)}^2}}, 试确定常数α的值,使Z服从t分布并确定自由度.

求指导本题解题过程，谢谢您！