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But what is the latest non-beta version of Sage?

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 = xyz - lam * (xyz-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

This is just a test, because I wrote a long and complex question and the forum wouldn't upload it.