2a. let a=1 and b-l find all values of a, b, c and d for which the matrices a and b commute? b. find all values of c for which the following matrix is invertible l1 1

we need to find the determinant.  

= -1(7*9 - 3* -3)(4*9 - 3*3) -2(4*9 -7*3)

= -1(63-27) +3 (36 - 9) -2( 36- 21)

= -1(36)+3(27)-2(15)

= -36+81-30

= 15

-362

step-by-step explanation:

(12)(4)+2(12)-34(12)+2(12)-3

  \/         \/         \/         \/

  48 +   24 -   408 + 24 - 3

      \   /               \   /

          72     -     432 - 3 = -363