(3)A4(i=1,2,…,s)可逆 5:00 例2 0:2 1/5:00 0;1 例3设Amm与Bn都可逆,Cmm,M= 求M 解detM=(det4)(detB)≠0=M可逆 XX A OX, X E O XX CB‖X3X O E AXI=E cX+BX,=0 CX+BX=E X4=B- 课后作业:习题二7(1)(3)(5),8(2)(4,10~1413 (3) A (i 1,2, ,s) i =  可逆                = − − − − 1 1 2 1 1 1 As A A A  例 2       =           = 2 1 0 2 1 0 3 1 5 0 0 O A A O A           −  = −      = − − − 0 2 3 0 1 1 1 5 0 0 1 2 1 1 1 O A A O A 例 3 设 Amm 与 Bnn 都可逆, Cnm ,       = C B A O M , 求 M −1 ． 解 detM = (detA)(detB)  0  M 可逆       = − 3 4 1 1 2 X X X X M ,        =            n m O E E O X X X X C B A O 3 4 1 2        + = + = = = n m CX BX E CX BX O AX O AX E 2 4 1 3 2 1        = = − = = − − − − 1 4 1 1 3 2 1 1 X B X B CA X O X A       − = − − − − 1 1 1 1 B CA B A O M 课后作业：习题二 7 (1) (3) (5), 8 (2) (4), 10～14