[ Eq(Derivative(x1, t), ((-1)*k14*k3*x3*x1 + 1*k14*k8*x4 + (-1)*k14*(k1 + k10)*x1 + 1*k9*x2/k2)/k14),
  Eq(Derivative(x2, t), (1*k10*x1*k2 + (-1)*k15*k9*x2)/k15),
  Eq(Derivative(x3, t), ((-1)*k14*k3*x3*x1 + 1*k14*k8*x4 + 1*k14*k7 + (-1)*k14*k6*x3)/k14),
  Eq(Derivative(x4, t), (1*k14*k3*x3*x1 + (-1)*k14*(k8 + k5)*x4)/k14) ]