西安毛子科技大学三XIDIAN UNIVERSITYXi专，由2)令X=·x,7tania12aina22anna21XAX =(xi,x)x..an1annXnan2."WWajx;a2jx;=(Xi,X2).,Xn)"Wiix1 2 , n x x X x     =       2) 令 由 11 12 1 1 21 22 2 2 1 2 1 2 ... ... ( , ,..., ) ... n n n n n nn n a a a x a a a x X AX x x x a a a x        =          1 1 2 1 2 1 1 ( , ,..., ) n j j j n j j n j n nj j j a x a x x x x a x = = =         =               