[ Eq(Derivative(x1, t), (1*k1*x2 + (-1)*k2*x1*x3)/k15),
  Eq(Derivative(x2, t), (1*k13*x7 + (-1)*k14*x2)/k15),
  Eq(Derivative(x3, t), (1*k3*x4 + (-1)*k4*x3)/k15),
  Eq(Derivative(x4, t), (1*k9*x1 + (-1)*k10*x6*x4)/k15),
  Eq(Derivative(x5, t), (1*k5*x2 + (-1)*k6*x3*x5)/k15),
  Eq(Derivative(x6, t), (1*k7 + (-1)*k8*x5*x6)/k15),
  Eq(Derivative(x7, t), (1*k11*x1 + (-1)*k12*x7)/k15) ]