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If A = [1234] and X is a 2 × 2 matrix such that AX = I, find X. - Mathematics and Statistics

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Question

If A = `[(1,2),(3,4)]` and X is a 2 × 2 matrix such that AX = I, find X.

Sum

Solution

We will reduce the matrix A to the identity matrix by using row transformations. During this process, I will be converted to matrix X.

We have AX = I

∴ `[(1,2),(3,4)] "X" = [(1,0),(0,1)]`

By R2 - 3R1, we get,

`[(1,2),(0,-2)] "X" = [(1,0),(-3,1)]`

By `(-1/2)`R2, we get,

`[(1,2),(0,1)] "X" = [(1,0),(3/2,-1/2)]`

By R1 - 2R2, we get,

`[(1,0),(0,1)] "X" = [(-2,1),(3/2,-1/2)]`

∴ X = `[(-2,1),(3/2,-1/2)]`

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Notes

The answer in the textbook is incorrect.

Elementry Transformations
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Chapter 2: Matrics - Miscellaneous exercise 2 (A) [Page 53]

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