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