Solution of a system with a parameter in the solution

[Gilles59]

(08-12-2017 06:00 PM)mazzeodalessio Wrote:  Hello guys. I have a big problem, which I can not solve. I bought a HP calculator, namely the HP Prime.
I took it especially because I have to solve several systems during a complex electronics exam, doing it all by hand would be crazy unfortunately.
(...)

I dont undestand how you get your result. If I'm not wrong you have a system of 5 equations (include 'Vu=5-250*I3' ) and 7 unknows (or 5 unknows and 2 parameters and you need 5 unknows and 1 parameter only to get 'Vu' in function of only 'Vi')

With the HP50G (exact mode) you can do :

Code:


['Vx=Vi-3*I1'
 'Vx=Vg+I2*5'
 'I1=I2+I3'
 'I3=(Vx-2*Vg)/10'
 'Vu=5-250*I3']

 ['Vu' 'I1' 'I2' 'I3' 'Vx' ]

 SOLVE (or LINSOLVE)

And you get :
Vu=(650*Vg-(250*Vi-95))/19

I guess you can use LINSOLVE on the PRIME CAS do do this.

Are you sure that there is no typo error in your message, or that you have not forgotten an equation ?

EDIT : I get your result if I assum Vg=3/4

EDIT 2 : With the Prime, assuming Vg=0.75, CAS mode :

Code:

linsolve( [Vx=Vi-3*I1,   Vx=Vg+I2*5,  I1=I2+I3,   I3=(Vx-2*Vg)/10,   Vu=5-250*I3, Vg=0.75],  [Vu,I1,I2,I3,Vx,Vg])

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