Question

Type the correct answer in each box. Find the elements of matrix A. help PLS!!

Answer 1

Answer:

a = 2

b = 11

c = 11

d = -2

Step-by-step explanation:

$\sf \left[\begin{array}{cc}a&b\\c&d \end{array}\right] *\left[\begin{array}{ccc} 22&11&7\\ 6&-9&-15 \end{array}\right] =\left[\begin{array}{ccc} 22a+6b&11a-9b&7a-15b\\22c+6d&11c-9d&7c-15d \end{array}\right]$

   $\sf \left[\begin{array}{ccc} 22a+6b&11a-9b&7a-15b\\22c+6d&11c-9d&7c-15d \\ \end{array}\right] =\left[\begin{array}{ccc} 110&-77&-151\\230&139&107 \\ \end{array}\right]$  

On comparing to right side, we get,

 22a + 6b = 110

Divide the entire equation by 2

   11a + 3b = 55  ------------(I)

 11a   - 9b  = -77  -------------(II)

Subtract equation (II) from (I)

       11a + 3b = 55

       11a - 9b = -77

      -      +        +     {Now subtract}

               12b = 132

                 b = 132/12

$\sf \boxed{\bf \ b = 11}$

Substitute the value of b in eqaution (I)

  11a + 3*11 = 55

  11a + 33   = 55

             11a = 55 - 33

             11a = 22

               a = 22/11

      $\sf \boxed{\bf \ a = 2}$

           22c + 6d = 230

Divide by 2

           11c + 3d = 115  -----------------(III)

           11c - 9d  = -139 ------------------(IV)

Subtract (IV) from (III)

           11c + 3d  = 115

           11c - 9d  = 139

           -     +         -      

                  12d  =  -24

                      d = -24/12

                     $\sf \boxed{\bf \ d = -2}$

Plugin d = - 2 in equation (III)

    11c + 3*(-2) = 115

     11c  - 6      = 115

                11c  = 115 + 6

               11c = 121

                  c = 121/11

                 $\sf \boxed{\bf \ c = 11}$