Equation Icon  d-E (t) = -1 − u(a )2 + 2⟨u,u ∕x⟩ ≤ -1 + 2⟨u,u ∕x⟩ ≤ 1- + 2-⟨u, u⟩ = -1 + 2-2E (t). (7.121 ) dt b2 b2 b2 a b2 a