# Equations solving on Matlab , 3 unkowns and 2 equations.

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Rana Önem on 29 May 2020
Commented: Rana Önem on 29 May 2020
v0=vf+ vfg*x;
u0=uf+ufg*x;
If we know vf,vfg,uf,ufg values how can I calculate x? Can you help me please?
Also there is this eq. m2*(he-u0)==m1*(he-u1); , we know he, m1,u1, values too.
In addition this eq. m2=v/vO; we know v value.

Robin Kirsch on 29 May 2020
if you have the 2 formulas m2 *(he... and m2 = v/v0 , dont you have 3 unknowns and 3 equations then? see my answer below
or is v0 of the first equation different from the m2 = v/vO?
Rana Önem on 29 May 2020
No it is not diffrent. I'm sorry my bad.

Robin Kirsch on 29 May 2020
If you simply want to know x, v0 and u0 you can just use the solve method. I assumed random variables for the known constants in my example.
syms x v0 u0
vf = 3;
vfg = 5;
uf = 2;
ufg = 1;
v = 7;
he = 2.5;
m1 = 4;
u1 = 1.1;;
eqn1 = v0 == vf+ vfg*x;
eqn2 = u0 == uf+ufg*x;
eqn3 = v/v0 * (he - u0) == m1*(he-u1);
[x v0 u0] = solve([eqn1, eqn2, eqn3], [x, v0, u0])

Rana Önem on 29 May 2020
When I write this on Matlab ,on Workspace for x it writes 1x1 sym, for v0 and u0 too. I click on it but it didn't gave me the number of x. What can I do now?
Brent Kostich on 29 May 2020
If you use 'syms' you get symbolic variables. They do not produce a numeric output. You can substitute numeric values for the syms to get a numeric output.
Rana Önem on 29 May 2020
Okay I'll try this, thank you so much!

R2017a

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