Can this be solved with any HP CAS?

[Csaba Tizedes]

(09-30-2017 01:04 PM)Gilles59 Wrote:  but we have a brain. A cas is just a tool. This limitation of DOMAIN for the 50g is explain in the doc.

Yes, my biggest problem is that, the English is not my native and I cannot explain subtly what I want to say. Of course I dont want to underestimate anybody here.
I stopped at 48GX, but I have an 48GII - as I know that is same as 50G, and found X=5.

(09-30-2017 01:04 PM)Gilles59 Wrote:  You are engineer. Why x=5 is impossible in a physical point of view? For an engineer mathematic is just a tool in my point of view.

This is my luck. The real problems are so smooth and has derivative in any point

Csaba