Question

6. Find the minors and cofactors of the third row, given 9 11 4 A= 3 27 6 10 4

Answer 1

A = Call ael 912 913 422 423 932 433 1931 R₃ 3X3 then 912 413 93 (m3) a minor of ( riding 922 923 3rd row and ist columm ) A- 01 9 3 6 9 7 2 lo 4 R3 - M31 = 77 - 8 = 69 2 7 M32 = 4 63-12 = 51 9 3 7 M33= 9 3 11 2 18-33 = -15 Now, co-factor of q;. Coj) = €150 mg . = 69 C31 = Eust 69 3+2 C32 = EU 51 = 3+3 C33 = EUⓇ (-15) -51 -15 - 4) (a) E = 4 7 - 2 3 0 2 0 = 2 LC31 E I adj le) TEL Now, (Expanding along R) TEI = 4 (3-0) +2°(7-0) + (0-6) 12 +14-6 = 20 T Adje al 42 43 where Ci C22 223 cij is the C32 C33J cofactor of ay: T 3 -7 2 (use definition ५ - 3 7 26 of cafactors, (see Prevby exam 3 -3 -7 7 -6 26 E' 1 - 3 20 -7. 2 7 -6 ។ 26 2 Adj (E)= 2 2 ५ .. 3 2 To 4-21 30 20 lo I 5 -3 20 7 20 13 lo lo A can be find by other three thui poo cers.