Explicit and implicit Euler Schems

i have the following system:

An explicit Euler scheme of the equations (0.1) and (0.2) give:

real t=0.0;

real dt=0.1;

real tau=1;

real n= tau/dt;

Vh U, I, Udecale, Idecale;

(Udecale -U)/dt = -k2UV


An Euler implicit scheme of the equation (0.3) is:

Vh V, Vold


My question is: How we can obtain three linear equations after using this schems? Is it possible?

Thank’s in advance.