If is the inverse of a matrix , then the sum of all values of for which , is :
- (A)0
- (B)-1
- (C)1✓ Correct
- (D)2
Answer: (C)
Solution
Since , we have , so . Expanding along its first row, . The condition means , hence , so , i.e. or . By Vieta's formulas the two values of add up to .
JEE Main · 2019 · 12 Apr 2019 · Shift 1 · Single correct option