Question Details

Given P = [pij]3 × 3 and Q = [qij]3 × 3 are 3 × 3 matrices, where qij = 2i + j – 1 pij. If |Q| = 210, then the value of |adj(adj(P))| is

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Correct Answer :

16

Solution :

The correct answer is 16.

Let us solve the problem step-by-step.
We are given two 3×3 matrices, P=[pij] and Q=[qij], such that:
qij=2i+j-1pij

Let us write the matrix Q explicitly in terms of the elements of P:
Q = [ q11 q12 q13 q21 q22 q23 q31 q32 q33 ] = [ 21p11 22p12 23p13 22p21 23p22 24p23 23p31 24p32 25p33 ]

Now, let us calculate the determinant of Q, denoted as |Q|:
|Q| = | 21p11 22p12 23p13 22p21 23p22 24p23 23p31 24p32 25p33 |

We can factor out common terms from the rows and columns of this determinant:
From row 1 (R1), take out a factor of 21.
From row 2 (R2), take out a factor of 22.
From row 3 (R3), take out a factor of 23.
This gives:
|Q| = 21·22·23 | p11 21p12 22p13 p21 21p22 22p23 p31 21p32 22p33 |

Next, we can factor out common terms from the columns:
From column 2 (C2), take out a factor of 21.
From column 3 (C3), take out a factor of 22.
This gives:
|Q| = (21·22·23) · (21·22) | p11 p12 p13 p21 p22 p23 p31 p32 p33 |

Simplifying the powers of 2 and identifying the remaining determinant as |P|:
|Q| = 21+2+3+1+2 · |P|
|Q| = 29 · |P|

We are given that |Q|=210. Substituting this value:
210 = 29 · |P|
Dividing both sides by 29:
|P| = 2

Now, we need to find the value of |adj(adj(P))|.
For a matrix A of order n×n, we have the standard property:
|adj(adj(A))| = |A|(n-1)2

Here, P is a 3×3 matrix, so n=3.
Substituting n=3 and |P|=2:
|adj(adj(P))| = |P|(3-1)2 = 222 = 24 = 16

Thus, the value of |adj(adj(P))| is 16.

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