[ Eq(Derivative(x1, t), ((-1)*k12*k6*x4*x1 + (-1)*k12*k8*x1 + 1*k12*k7)/k12),
  Eq(Derivative(x2, t), ((-1)*k12*k4*x3*x2 + (-1)*k12*k2*x2 + 1*k12*k3)/k12),
  Eq(Derivative(x3, t), (1*k12*k9*x4 + (-1)*k12*k10*x3 + (-1)*k12*k11*x3 + (-1)*k12*k4*x3*x2)/k12),
  Eq(Derivative(x4, t), ((-1)*k12*k9*x4 + 1*k12*k10*x3 + (-1)*k12*k5*x4 + (-1)*k12*k6*x4*x1)/k12),
  Eq(Derivative(x5, t), 1*k12*k11*x3/k12) ]