{ diff(x1, t) = (1*k7 + (-1)*x1*k8*x2*(x1 + k9)^(-1) + (-1)*x1*k10 + (-1)*k17*x1*x4 + 1*k18*x5 + 1*k19*k20*x5)/k6,
  diff(x2, t) = (1*x3*k5*(1 + (-1)*x2)*(k14 + (-1)*x2 + 1)^(-1) + (-1)*k16*x2*(k15 + x2)^(-1))/k6,
  diff(x3, t) = (1*(1 + (-1)*x3)*x1*k3*(x1 + k2)^(-1)*(k11 + (-1)*x3 + 1)^(-1) + (-1)*x3*k12*(k13 + x3)^(-1))/k6,
  diff(x4, t) = ((-1)*k17*x1*x4 + 1*k18*x5 + 1*k22*k21*x5 + 1*k23 + (-1)*k24*x4)/k6,
  diff(x5, t) = (1*k17*x1*x4 + (-1)*k18*x5 + (-1)*k19*k20*x5 + (-1)*k22*k21*x5)/k6 }