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  1. GATE CS
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  3. Engineering Mathematics

Perform the following operations on the matrix M = [[3, 4, 45], [7, 9, 105], [13, 2, 195]]: i. Add the third row to the second row. ii. Subtract the third column from the first column. The determinant of the resultant matrix is ___________.

GATE 2015 · Engineering Mathematics · Matrix · easy

Answer: det = 0

  1. Check linear dependence of original matrix M: Column 3 = 15 * Column 1: [45,105,195] = 15 * [3,7,13]. Therefore columns 1 and 3 are linearly dependent.
  2. Apply elementary operations - determinant unchanged: Operation i (R2 <- R2+R3) and Operation ii (C1 <- C1-C3) are both elementary operations that preserve the determinant. So det(resultant matrix) = det(M) = 0.