passwella.
Menu

JAMB Mathematics 2009 Question 21

Question 21

Binary Operations

A binary operation ⊗ defined on the set of integers is such that m ⊗ n = m + n + mn for all integers m and n. Find the inverse of −5 under this operation, if the identity element is 0.

  1. A.−5/4
  2. B.−5/6
  3. C.0
  4. D.5
Show the answer and explanation

Answer: A (−5/4)

Explanation

−5 ⊗ a = 0 gives −5 + a − 5a = 0, so −4a = 5 and a = −5/4.