Newbie: Simplifying equations as specified

I'm learning Maxima by exercising on an old problem (propagation of error).
I solve for a function I want using the commands listed at the bottom of
this message. Then, I'd like to simplify in a specific way to ease
transferring the result into a statistical program. I've read through the
documentation several times and obtained various error messages over the
last 48 hours but the solution to my exercise eludes me. Sorry, but I've
never used LISP. Help. 

Commands:
f(a,b):=1-a/b;
g(a,b,sa2,sb2,f):=sa2*diff(f,a)^2+sb2*diff(f,b)^2;
r:f(u,v);
sr2:g(u,v,su2,sv2,r);
u:f(w,x);
v:f(y,z);
su2:g(w,x,sw2,sx2,u);
sv2:g(y,z,sy2,sz2,v);
ev(r);
ev(sr2);

Desired simplifications:
(1) Expressions of u and v in w, x, y, and z back into u and v
(2) sx2/x^2=cvx2
(3) sw2=cvw^2/w^2