JEE Advanced2024Paper 1MATH-III
Q.
Let , where denotes the determinant of . Then the number of elements in is ______.
Correct answer: 16
Solution
Expanding along the first row, , which must be with all entries in .
Case 1: . Then . With , the pairs are or , giving 2 choices. The entries are free in , giving choices. Total: .
Case 2: . Then . We need integer pairs from summing to . The valid combinations are:
. Each value for a difference can come from or (2 ways), while has 1 way each.
Counting: ; ; ; . Total: .
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