6 ( i = 1 k α i λ i 3 ) ( 3 ( 2 ( i = 1 k α i λ i 2 ) ( i = 1 k α i λ i ) 2 ) + ( i = 1 k α i λ i ) 2 ) ( i = 1 k α i λ i ) ( 2 ( i = 1 k α i λ i 2 ) ( i = 1 k α i λ i ) 2 ) 3 2