=x”A→元=(x”A)=x”Ax -元=2lm(2)=x”(A-A)x=x“(A-A)x 将x写成x=[5,52,…,5n] x(4-4)x=∑∑，(a,-a)5 2m(2-2空a,-a,片 ≤2∑E.(a,-a)5 3H λ = x Ax → ( ) H H H H λ = = x Ax x A x 2 Im( ) ( ) ( ) H HH T λλ λ −= = − = − j x AA xx AAx 将 x 写成 [ 1 2 ,,, ] T n x = ξξ ξ  ( ) ( ) 1 1 n n H T i ij ji j i j x AAx a a ξ ξ = = −= − ∑∑ ( ) ( ) ( ) 1 1 1 1 2 Im n n i ij ji j i j n n i ij ji j i j a a a a λξ ξ ξ ξ = = = = = − ≤ − ∑∑ ∑∑ 3