JEE Main 2026 Mathematics question
Let be a set of 2 × 2 matrices. Then the number of matrices in S, for which the sum of the diagonal elements is equal to 4, is:
Answer: (D)
Solution
By Cayley–Hamilton, trace = 4 and det = 3 automatically satisfy A² − 4A + 3I = 0. With a + d = 4: pairs (a,d) = (1,3),(3,1) need bc = ad−3
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