1234
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Determinants for 3x3's - Method 1

Here's another one...  We just need to be careful with the negatives, so write out all your work really neatly!

| top row: 6 , -2 , 3 middle row: -5 , 4 , 0 bottom row: -7 , 8 , 1 |

| top row: 6 , -2 , 3 middle row: -5 , 4 , 0 bottom row: -7 , 8 , 1 | outside top row: 6 , -2 outside middle row: -5 , 4 outside bottom row: -7 , 8 ... multiply the 6 , 4 , and 1 ... + ... multiply the -2 , 0 , and -7 ... + ... multiply the 3 , -5 , and 8 ... +










| top row: 6 , -2 , 3 middle row: -5 , 4 , 0 bottom row: -7 , 8 , 1 | outside top row: 6 , -2 outside middle row: -5 , 4 outside bottom row: -7 , 8 ... multiply the -7 , 4 , and 3 ... - ... multiply the 8 , 0 , and 6 ... - ... multiply the 1 , -5 , and -2 ... -


= ( 6 ) ( 4 ) ( 1 ) + ( -2 ) ( 0 ) ( -7 ) + ( 3 ) ( -5 ) ( 8 ) - ( -7 ) ( 4 ) ( 3 ) - ( 8 ) ( 0 ) ( 6 ) - ( 1 ) ( -5 ) ( -2 )


= 24 + 0 - 120 + 84 - 0 - 10 = -22

YOUR TURN:

... and I'll give you a big hint:
                  The answer should be -348 !


| top row: -2 , 8 , 6 middle row: 4 , 1, 0 bottom row: -5 , -3 , 9 |