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Correct Answer :

117

Solution :

The correct answer is 117.

Step 1: Identify the given matrices and conditions
We are given the 3 × 3 matrix A:

A = [ 2 1 0 0 0 1 1 0 0 ]
and the matrix B defined by its columns:

B = [ B1 B2 B3 ]
The columns satisfy the following linear equations:

A · B1 = [ 2 3 1 ] , A B2 = [ 2 0 0 ] , A B3 = [ 3 2 1 ]

Step 2: Find the inverse of matrix A
To determine the column vectors of B, we can compute the inverse matrix of A, denoted as A-1.
Let us solve the system AX=Y where:

[ 2 1 0 0 0 1 1 0 0 ] [ x1 x2 x3 ] = [ y1 y2 y3 ]
This gives the system of equations:
1) 2x1+x2=y1
2) x3=y2
3) x1=y3

Solving for x1, x2, and x3 in terms of y1, y2, and y3:
x1=y3
x2=y1-2y3
x3=y2

Therefore, the inverse matrix A-1 is:

A-1 = [ 0 0 1 1 0 -2 0 1 0 ]

Step 3: Determine the column vectors of B
Now we calculate B1, B2, and B3:

B1 = A-1 [ 2 3 1 ] = [ 0(2)+0(3)+1(1) 1(2)+0(3)-2(1) 0(2)+1(3)+0(1) ] = [ 1 0 3 ]

B2 = A-1 [ 2 0 0 ] = [ 0(2)+0(0)+1(0) 1(2)+0(0)-2(0) 0(2)+1(0)+0(0) ] = [ 0 2 0 ]

B3 = A-1 [ 3 2 1 ] = [ 0(3)+0(2)+1(1) 1(3)+0(2)-2(1) 0(3)+1(2)+0(1) ] = [ 1 1 2 ]

Thus, the matrix B is:

B = [ 1 0 1 0 2 1 3 0 2 ]

Step 4: Compute the determinant and trace of B
1. Determinant of matrix B (α=|B|):
We expand along the first row:
|B| = 1 · | 21 02 | - 0 + 1 · | 02 30 |
|B| = 1 ( 4 - 0 ) + 1 ( 0 - 6 ) = 4 - 6 = - 2
So, α=-2.

2. Diagonal sum (trace) of matrix B (β):
β = 1 + 2 + 2 = 5

Step 5: Calculate the final value
We need to find the value of α3+β3:

α3 + β3 = (-2)3 + 53
α3 + β3 = - 8 + 125 = 117

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