How to Find a Determinant of a Matrix

Find Determinant of 2x2 Matrix

• 1

  Label each of the four numbers in the matrix "A" through "D," starting in the upper left and moving left to right, top to bottom.

• 2

  Multiply numbers A and D together and multiply numbers B and C together.

• 3

  Subtract the result of B times C from A times D. This result is the determinant of your 2x2 matrix.

Find Determinant of 3x3 Matrix

• 4

  Label each of the nine numbers in your matrix "A" through "I," starting in the upper-left corner and moving left to right, top to bottom.

• 5

  Perform the following multiplications and subtractions on the following sets of numbers (where the asterisk symbol represents a multiplication sign):
  A*(E*I - H*F)
  D*(B*I - H*C)
  G*(B*F - E*C)
  Call these three sets of numbers "X," "Y" and "Z," respectively.

• 6

  Perform the following subtraction, using the numbers you arrived at in Step 2: X-Y-Z. This final result is the determinant of your 3x3 matrix.