A non-singular matrix M = bmatrix 3 & 6 & 96 & 9 & 129 & 12 & 18bmatrix is such that M-¹ = bmatrix -2/3 & 0 & 1/30 & 1 &
From the definition, after simplifying, -2 is left. The method is simple: formula → substitution → calculation → answer.
Ref: NCERT Mathematics Class XII — Matrices and Determinants
