Binary Operations - Jamb Mathematics Past Questions and Answers

Question 36:

• JAMB 2008

A binary operation * is defined on the set of positive integers is such x*y = 2x-3y+2 for all positive integers x and y. The binary operation is

A. Commutative and close on the set of positive integers
B. Neither commutative nor closed on the set of ppositive integers
C. Commutative but not closed on the set of positive integers
D. Not cummutative but closed on the set of positive integers

Question 37:

• JAMB 2008

A binary operation on the real set of numbers excluding -1 is such that for all m, n ∈ R, mΔn = m+n+mn. Find the identity element of the operation.

A. 1
B. Zero
C. -¹/₂
D. -1

Question 38:

• JAMB 2009

If m * n = n - (m+2) for any real number m and n find he value of 3*(-5)

A. -6
B. -8
C. -10
D. -12

Question 39:

• JAMB 2009

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

A. -⁵/₄
B. -⁵/₆
C. Zero
D. 5

Question 40:

• JAMB 2010

If x * y = x + y², find then value of (2*3)*5

A. 36
B. 25
C. 11
D. 55