Circuit Theory/Source Injection/code

numeric::linsolve([ (1-va)/2 - (va-vb)/4 - va/5, (1-vb)/3 + (va-vb)/4 - vb/6, current = (1-va)/2 + (1-vb)/3],[va,vb,current])

[va = 0.7051282051, vb = 0.6794871795, current = 0.2542735043]

current = 0.2542735043; vs = 1; Req = vs/current