# 12

> ode1 := diff( R(t), t ) = 4*R(t) - 7*F(t) - 1 ;

> ode2 := diff( F(t), t ) = 3*R(t) + 6*F(t) - 12 ;

> MODEL := { ode1, ode2 } ; # define the differential equation model

> VAR := { R(t), F(t) } ; # identify the variables in the model in the form h(t), u(t)

>

(a) -- Equilibrium Solutions

(b) -- Direction Field

(c) -- Phase Portrait