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JAMB Mathematics 2012 Question 22

Question 22

Binary Operations

A binary operation on the set of real numbers is defined by m * n = mn/2 for all m, n ∈ R. If the identity element is 2, find the inverse of −5.

  1. A.−4/5
  2. B.−2/5
  3. C.4
  4. D.5
Show the answer and explanation

Answer: A (−4/5)

Explanation

The inverse a satisfies −5a/2 = 2, so a = −4/5.