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Question
Using Cofactors of elements of second row, evaluate `triangle = |(5,3,8),(2,0,1),(1,2, 3)|`
Solution
The co-sections of the second row will be like this:
`A_21 = (-1)^(2 + 1) abs ((3,8),(2,3)) = (-1) xx [3 xx 3 - 2 xx 8] = 7`
`A_22 = (- 1)^(2 + 2) abs ((5,8),(1,3)) = 1 [5 xx 3 - 1 xx 8] = 7`
`A_23 = (-1)^(2 + 3) abs ((5,3),(1,2)) = (-1) [5 xx 2 - 3 xx 1] = - 7`
`therefore Delta = a_21 * A_21 + a_22 * A_22 + a_23 * A_23`
`= 2 xx 7 + 0 xx 7 + 1 xx (- 7)`
`= 14 - 7 = 7`
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