{ diff(x1, t) = ((-1)*k8*x3*x1*1/(k9 + x1)*k2 + (-1)*k1*k14*x6*1/(k15 + x6)*k3 + (-1)*k1*k16*x1*1/(k17 + x1)*k3)/k2,
  diff(x2, t) = ((-2)*(k4*x2^2 + (-k5*x4))*k2 + 1*k8*x3*x1*1/(k9 + x1)*k2)/k2,
  diff(x4, t) = (1*(k4*x2^2 + (-k5*x4))*k2 + (-1)*k12*x4*1/(k13 + x4)*k3)/k2,
  diff(x5, t) = (1*(k10*x7^2 + (-k11*x5))*k1 + 1*k12*x4*1/(k13 + x4)*k3)/k1,
  diff(x6, t) = (1*k6*x8*x7*1/(k7 + x7)*k1 + 1*k1*k14*x6*1/(k15 + x6)*k3 + 1*k1*k16*x1*1/(k17 + x1)*k3)/k1,
  diff(x7, t) = ((-1)*k6*x8*x7*1/(k7 + x7)*k1 + (-2)*(k10*x7^2 + (-k11*x5))*k1)/k1,
  diff(x8, t) = 0/k1,
  diff(x9, t) = 1*k8*x3*x1*1/(k9 + x1)*k2/k2 }