=(/-S,f-S)=(f,f-S)-(S,f-S (f,f)-(S,f)-(S,f-S 由 于 akp k=0 ∑a(,-∑ k=0 ∑a(,qk)-∑(129k)) 所以 162=(f-S,f-S)=(/,)-(S2 * * * * * 2 = − − = − − − ( , ) ( , ) ( , ) f S f S f f S S f S * * * = − − − ( , ) ( , ) ( , ) f f S f S f S 由 于 * * * * 0 0 ( , ) ( , ) n n k k j j k j S f S a f a = = − = − * * 0 0 ( , ) n n k k j j k j afa = = = − * * 0 0 (( , ) ( , ) ) 0 n n k k j k j k j a f a = = = − = 所以 ( , ) ( , ) ( , ) * * * 2 2 = f − S f − S = f f − S f