[ Eq(Derivative(x1, t), ((-1)*k7*k4*k5*x1*x3/x5 + 1*k7*k2*x4)/k7),
  Eq(Derivative(x2, t), (1*k7*k4*k5*x1*x3/x5 + (-1)*k7*k3*x2)/k7),
  Eq(Derivative(x3, t), (1*k7*k3*x2 + (-1)*k7*k4*x3)/k7),
  Eq(Derivative(x4, t), (1*k7*k4*x3 + (-1)*k7*k2*x4)/k7),
  Eq(Derivative(x5, t), 0/k7) ]