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