设随机变量X的概率分布为……求EX,DX,E（X－1）^2

EX=1/3+1/3+1/2+1+7/6=
EX^2=1/3+2/3+3/2+6+49/6=
DX=EX^2-(EX)^2=
D(X-1)=DX
E(X-1)=EX-1
E(x-1)^2=D(X-1)+(E(X-1))^2