Let A be a 3 × 3 matrix such that A+ A^ T= O. If A [ … ] and det( adj(2 adj( ~A+ I)))=(2)^α ·(3)^β ·(11)^γ, α, β, γ are non-negative integers, then…
JEE Main 2026 — Mathematics Algebra
2026integerhard
Let A be a 3×3 matrix such that A+AT=O. If A1−10=332,A21−10=−319−24 and det(adj(2adj(A+I)))=(2)α⋅(3)β⋅(11)γ,α,β,γ are non-negative integers, then α+β+γ is equal to ____
Official previous-year question
Held on 22 Jan 2026 · Verified 6 Jul 2026.
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Solution
A is skew-symmetric: A=0c−b−c0ab−a0.
From A1−10=332: c=3, a+b=−2.
From A21−10=−319−24: b=3, a=−5.
A+I=13−3−31−5351, det(A+I)=44.
For 3×3 matrix: det(adj(M))=(detM)2.
det(2adj(A+I))=8⋅442=8⋅1936=15488=27⋅112.
det(adj(2adj(A+I)))=154882=214⋅114.
α=14,β=0,γ=4. α+β+γ=18.
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