### solving systems of equations returns [] Redux

I searched the wiki and found the "solve always returns []" question. But it doesn't help me. I will admit that I am a complete neophyte with Sagemath and have been playing with version 7.2 on my windows machine.

I was trying to do something very simple: solve a basic Lagrange Multiplier problem, so I defined the following:

- var('x' ,'y' ,'z', 'lam')
- var('F')
- F = x
*y*z - lam * (x*y*z-9) - var('dFx', 'dFy', 'dFz', 'dFlam')
- dFx=diff(F,x)
- dFy=diff(F,y)
- dFz=diff(F,z)
- dFlam=diff(F,lam)
- solve([dFx==0,dFy==0,dFz==0,dFlam==0],x,y,z,lam)

but the **solve** returns []. It should return something like x==3, y==3, z==3, shouldn't it? Is there an alternative way to approach this?

Thanks.

BobM