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If A  , find k so that , where I is an identity matrix.

  1. 4
  2. 5
  3. 6
  4. 7

Answer (Detailed Solution Below)

Option 4 : 7
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Detailed Solution

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Concept:

If A and B are two matrices such that the no. of columns of A is equal to the no. of rows of B. If A = [aij] is a m × n matrix and B = [bij] be a n × p matrix, then the product AB is the resultant matrix of order m × p and is defined as:

Calculation:

Given: A 

Here, we have to find the value of k such that 

As the two matrices are equal, their corresponding elements are also equal.

Comparing the corresponding elements:

4k = 28 

⇒ k = 7

∴ The value of k is 7.

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