例2设x∈P",A∈P",则Am,是与x2 相容的矩阵范数 证‖Ax=∑ ;1x1+a2;x+…+a ≤∑(∑1ar2)(∑|x;2) C∑|an12)·∑|x2 L=lJ =An,‖xl例 2 相容的矩阵范数. 2 , || || || || 2 x P A P A m x 设  n  nn ，则 是与 证 2 2 || Ax ||  = = + + + n i i i i n n a x a x a x 1 2 1 1 2 2 |  | ( | | ) ( | | ) 1 1 1 2 2    = = =  • n i n j n j aij x j   = = = = • n i n j n j ai j x j 1 1 1 2 2 ( | | ) | | 2 2 2 || || || || 2 = A m • x