{ diff(x1, t) = (1*(k1*(1 + k15*k20*(x11 + x12)) - k3*(1 + k18*k15)*x1) + (-2)*(k7*x1^2*x4^2 - k10*x5) + (-2)*(k8*x1^2*x2 - k11*x3))/k26,
  diff(x2, t) = ((-1)*(k8*x1^2*x2 - k11*x3) + (-1)*(k16*x2*x13 - k17*x14))/k26,
  diff(x3, t) = 1*(k8*x1^2*x2 - k11*x3)/k26,
  diff(x4, t) = ((-2)*k5*x4^2 + (-2)*(k7*x1^2*x4^2 - k10*x5) + (-1)*k9*x4*x7 + 2*k6*x6)/k26,
  diff(x5, t) = 1*(k7*x1^2*x4^2 - k10*x5)/k26,
  diff(x6, t) = (1*k5*x4^2 + 1*k12*x8^2 + (-1)*k6*x6)/k26,
  diff(x7, t) = (1*(k2*(1 + k15*x5) - k4*x7) + (-1)*k9*x4*x7 + 2*k12*x8^2)/k26,
  diff(x8, t) = (1*k9*x4*x7 + (-2)*k12*x8^2)/k26,
  diff(x9, t) = 0/k26,
  diff(x10, t) = 0/k26,
  diff(x11, t) = 1*(k13*(1 + k19*k15) - k14*(x3/(k21 + x3) + x14/(k22 + x14) - x5/(k23 + x5))*x11)/k26,
  diff(x12, t) = 0/k26,
  diff(x13, t) = (-1)*(k16*x2*x13 - k17*x14)/k26,
  diff(x14, t) = 1*(k16*x2*x13 - k17*x14)/k26 }