n n nn n n n n n n b x a x a x a b x a x a x a b x a x a x a · + + + · + + + · + + + ..... ... ..... ..... 2 2 1 1 2 2 2 22 1 21 1 1 2 12 1 11 ¹ ¹ ¹ ¹ ¹ ) ¹ ¹ ¹…
