If A = [ array*20c 1&3 + x&2 1 - x&2&y + 1 2&5 - y&3 array ] is a symmetric matrix, then 3x + y is equal to?
We can see that after simplifying, -1 is left. The method is simple: formula → substitution → calculation → answer.
Ref: NCERT Mathematics Class XII — Matrices and Determinants
