[ Eq(Derivative(x1, t), (1*k9*k1*(1 + Piecewise((13/5, And(Gt(t, 10), Lt(t, 150))), (0, True)) + k5*(x2/k6)**4/(1 + (x2/k6)**4)) + (-1)*k9*k2*x1*k8)/k9), Eq(Derivative(x2, t), (1*k9*k3*x1*k8 + (-1)*k9*k4*x2*k8)/k9) ]