Given that the joint probability Pr(w,x,y,z) over four variables factorizes as
Pr(w,x,y,z) = Pr(w) Pr(z|y) Pr(y|x,w)Pr(x)
show that x is independent of w by showing that Pr(x,w) = Pr(x)Pr(w).
Attempt: if we simply assume Pr(x,w) = Pr(x)Pr(w), then:
\begin{align}
Pr(w,x,y,z) &= Pr(w)...