8-4 A=-81-44正交吗?不正交 1/9-8/9-4/9 A=-8/91/9-4/9,A1=?An 4/9-4/97/9 1-8-4 A 81-4.,A B 9→B-1 B T 9 →B1=9A1→A B 81?, 9/79/49/4 9/49/19/8 9/49/89/1 1 = ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎝ ⎛ −− − − −− = − A A T A ?, 744 418 481 1 = ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎝ ⎛ −− −− −− = − A A TT ABBAB 9 1 9 1 1 ==⇒= − T ABAAB 81 1 9 1 9 111 1 −−− − ==⇒=⇒ A , A正交吗？ 744 418 481 ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎝ ⎛ −− −− −− = 不正交