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Construct the matrix A = [aij]3×3 where aij = i − j. State whether A is symmetric or skew-symmetric.

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Question

Construct the matrix A = [aij]3 × 3 where aij = i − j. State whether A is symmetric or skew-symmetric.

Sum
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Solution

A = [aij]3 × 3  = `[("a"_11, "a"_12, "a"_13),("a"_21, "a"_22, "a"_23),("a"_31, "a"_32, "a"_33)]`

Given that: aij = i − j

∴ a11 = 1 − 1 = 0,

a12 = 1 − 2 = − 1,

a13 = 1 − 3 = − 2,

a21 = 2 − 1 = 1,

a22 = 2 − 2 = 0,

a23 = 2 − 3 = − 1,

a31 = 3 − 1 = 2,

a32 = 3 − 2 = 1,

a33 = 3 − 3 = 0.

∴ A = `[(0, -1, -2),(1, 0, -1),(2, 1, 0)]`

∵ aij = − aij for all i and j

∵ A is a skew-symmetric matrix.

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Chapter 4: Determinants and Matrices - Exercise 4.4 [Page 83]

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