Figure 4.5.

System (1.2) with combining treatment, i.e., when f_a = f_b = 0, f_ab = 1, we choose the same parameters Λ = 10, d = 1, b = 1, q = 0.1, s = 0.3, c = 1.5, h = 0.2, the same initial values x(0) = 0.45, y_w (0) = 1.5, y_a(0) = 1.0, y_b(0) = 0.5, y_ab(0) = 1.6, and let r_w, r_a, r_b, r_ab and h vary such that R₀ > 1. (i) When r_ab < min{r_w + h, r_a + h, r_b + h}, the semitrivial equilibrium E_ab is stable; (ii) when r_a + h < min{r_w + h, r_b + h, r_ab}, the semitrivial equilibrium E_a,ab is stable; (iii) when r_b + h < min{r_w + h, r_a + h, r_ab}, the semitrivial equilibrium E_b,ab is stable; (iv) when r_w + h < min{r_a + h, r_b + h, r_ab}, the semitrivial equilibrium E_w,ab is stable.