This problem requires a strong grasp of the properties of determinants and adjoints of matrices. We will systematically break down the given determinant expressions using these properties to solve for the unknown values.
Key Concepts and Formulas Used (for a square matrix X of order n=3 and a scalar k):
- Determinant of a scalar multiple: det(kX)=kndet(X)=k3det(X)
- Determinant of an adjoint matrix: det(adj(X))=(detX)n−1=(detX)2
- Adjoint of a scalar multiple: adj(kX)=kn−1adj(X)=k2adj(X)
- Adjoint of an adjoint matrix: adj(adj(X))=(detX)n−2X=(detX)X (since n−2=1)
Let D=detA for simplicity. Since A is a non-singular matrix, D=0.
Step-by-Step Solution:
We are given two equations involving determinants and need to find the value of ∣3m+2n∣.
Part 1: Analyzing the First Equation to find detA
The first equation is det(3adj(2adj((detA)A)))=3−13⋅2−10.
Let's simplify the expression from the innermost part outwards:
- Innermost term: (detA)A=DA. This is a scalar D multiplied by matrix A.
- Second innermost determinant (argument of outer
adj): adj(DA)
Using property 3, adj(kX)=k2adj(X), with k=D and X=A:
adj(DA)=D2adj(A)
- Third innermost determinant (argument of outermost
adj): 2adj(DA)
Substitute the result from step 2:
2(D2adj(A))=2D2adj(A)
- Outermost adjoint: adj(2D2adj(A))
Using property 3 again, adj(kX)=k2adj(X), with k=2D2 and X=adj(A):
adj(2D2adj(A))=(2D2)2adj(adj(A))
=4D4adj(adj(A))
Now, using property 4, adj(adj(A))=DA:
=4D4(DA)=4D5A
- Argument of the outermost determinant: 3adj(2adj(DA))
Substitute the result from step 4:
3(4D5A)=12D5A
- Final determinant evaluation: det(12D5A)
Using property 1, det(kX)=k3det(X), with k=12D5 and X=A:
det(12D5A)=(12D5)3det(A)
=123(D5)3D=123D15D=123D16
We know 12=22⋅3, so 123=(22⋅3)3=26⋅33.
Thus, the LHS simplifies to 26⋅33⋅D16.
Now, equate this to the given value:
26⋅33⋅D16=3−13⋅2−10
To find D16, divide both sides by 26⋅33:
D16=26⋅333−13⋅2−10
D16=2−10−6⋅3−13−3
D16=2−16⋅3−16
D16=(2⋅3)−16=6−16
From this, D=detA=±6−1. For the subsequent calculations, D2 will be used, which is unique:
D2=(6−1)2=6−2
Part 2: Analyzing the Second Equation to find m and n
The second equation is det(3adj(2A))=2m⋅3n.
Let's simplify the expression from the innermost part outwards:
- Innermost term (argument of
adj): 2A
- Adjoint term: adj(2A)
Using property 3, adj(kX)=k2adj(X), with k=2 and X=A:
adj(2A)=22adj(A)=4adj(A)
- Argument of the outermost determinant: 3adj(2A)
Substitute the result from step 2:
3(4adj(A))=12adj(A)
- Final determinant evaluation: det(12adj(A))
Using property 1, det(kX)=k3det(X), with k=12 and X=adj(A):
det(12adj(A))=123det(adj(A))
Using property 2, det(adj(A))=(detA)2=D2:
=123D2
Substitute 123=26⋅33:
=26⋅33⋅D2
Now, substitute the value of D2=6−2 found in Part 1:
=26⋅33⋅(6−2)
Since 6−2=(2⋅3)−2=2−2⋅3−2:
=26⋅33⋅2−2⋅3−2
Combine the powers of 2 and 3:
=26−2⋅33−2
=24⋅31
This expression is given as 2m⋅3n.
Therefore, by comparing the powers:
m=4
n=1
Part 3: Calculating the Final Value
We need to find ∣3m+2n∣.
Substitute the values of m and n:
∣3m+2n∣=∣3(4)+2(1)∣
=∣12+2∣
=∣14∣
=14
The final answer is 14.
Summary and Key Takeaway:
This problem demonstrates the importance of meticulously applying the properties of determinants and adjoints. By systematically simplifying the expressions from the innermost operations outwards, we avoided errors. The key properties for an n×n matrix are det(kX)=kndet(X) and det(adj(X))=(detX)n−1. Additionally, the property adj(kX)=kn−1adj(X) is crucial for simplifying complex adjoint arguments. Careful tracking of powers of scalars is essential to arrive at the correct final answer.