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UI Post-UTME Mathematics 2025 (Model questions) Question 24

Question 24

Binary Operations

Find the identity element for an operation defined by: a * b = ab − a − b + 2

  1. A.0
  2. B.1
  3. C.2
  4. D.3
Show the answer and explanation

Answer: C (2)

Explanation

We need a * e = a: ae − a − e + 2 = a, i.e. (a − 1)(e − 2) = 0 for all a, so e = 2.