3x3Determinants

3x3Determinants - And again, the product of the 3 numbers...

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By: Kristi King
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There are short cut methods of finding the determinant for the 2x2 matrix and the 3x3 matrix. All square matrices of size 4 and above must use the Cofactor and Minors method of finding the determinant.
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We will use the same example that is in the notes: - 2 1 1 4 1 3 0 1 2 Example From the notes we already know the answer is -14 Here is the easy way to arrive at that answer : 1 1 1 3 1 2 2 1 1 4 1 3 0 1 2 - - Step 1: Copy column 1 and 2 next to the matrix .
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Step 2: Beginning with 2, multiply the numbers on the diagonal (3 numbers only). To that add the product of the 3 numbers on the next diagonal.
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Unformatted text preview: And again, the product of the 3 numbers on the last diagonal . Now beginning with the 1 in the upper right hand corner, we are going to come back, multiplying the numbers on the diagonals. We will also sum these and then subtract the answer from the sum above. 1 1 1 3 1 2 2 1 1 4 1 3 1 2- -1 1 1 3 1 2 2 1 1 4 1 3 1 2- -1(3)(2) ) )( ( 1 4 2 + 14 8 6 1 1 = + + =-+ ) )( ( Now subtract: 0 - 14 = - 14 (2)(-1)( 2) + (1)(4)(1) +(0)(3)(1)=-4+4+0=0...
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This note was uploaded on 02/13/2011 for the course MAT 3321 taught by Professor Yuan during the Spring '11 term at Texas Wesleyan.

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3x3Determinants - And again, the product of the 3 numbers...

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