How to find adjoint or cofactor of a matrix in less than a minute

Calculating adjoint or cofactor of matrix is a time taking process. And solving these may cost you lot of time.If u follow the below steps you can easily solve the problem in less than a minute.

Step 1:

Start by analysing the square matrix. lets take a look at the example given below:

Step 2:

Write the matrix four times to form a square .2 matrix side by side and 2 below them as shown below:

Step 3:

Cut the numbers on the outside of the numbers on 4 sides as shown below:

Step 4:

Multiply the first number with the second number on next row and subtract it with the product of the next number on first row with the first num as shown in example . the result is the first number on our cofactor matrix.

  • number 1 on cofactor matrix: 6*7 - 3*1 = 42-3 = 39
  • number 2 on cofactor matrix: 3*2 - 5*7 = 6-35 = -29
  • number 3 on cofactor matrix: 5*1 - 6*2 = 5-12 = -7
  • number 4 on cofactor matrx: 1*5 - 7*8 = 5-56 = -51
  • number 5 on cofactor matrix: 7*4 - 2*5 = 28-10 = 18
  • number 6 on cofactor matrix: 2*8 - 1*4 = 16-4 = 12
  • number 7 on cofactor matrix: 8*3 - 5*6 = 24-30 = -6
  • number 8 on cofactor matrix: 5*5 - 4*3 = 25-13 = 12
  • number 9 on cofactor matrix: 4*6 - 8*5= 24-40 = -16

Step 5:

Write the numbers on the matrix to get the cofactor of the matrix. The cofactor of our matrix is

Step 6:

Write the cofactor's numbers on a different arrangement to form adjoint of the matrix with column1 of cofactor as row1 and column2 as row 2 etc. The adjoint of the matrix is:

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