Binary Operations - Jamb Mathematics Past Questions and Answers

Question 31:

• JAMB 2005

An operation * is defined on the set of real numbers by a * b = ab + 2(a + b + 1). find the identity element

A. 2
B. 1
C. -1
D. -2

Question 32:

• JAMB 2006

A binary operation \(\oplus\) defined on the set of real number is such that x\(\oplus\)y = xy/6 for all x, y ∈ R. Find the inverse of 20 under this operation when the identity element is 6

A. ¹/₁₂
B. ¹⁰/₃
C. ¹/₂₀
D. ⁹/₅

Question 33:

• JAMB 2006

A binary operation * on the set of rational numbers is defined as \(x \ast y = \frac{x^2 - y^2}{2xy}\). Find \(-5 \ast 3\)

A. \(\frac{-8}{15}\)
B. \(\frac{8}{15}\)
C. \(\frac{17}{15}\)
D. \(\frac{-17}{15}\)

Question 34:

• JAMB 2007

A binary operation ⊕ on real numbers is defined by x ⊕ y = xy + x + y for any two real numbers x and y. The value of (-³/₄) ⊕ 6 is

A. ³/₄
B. -⁹/₂
C. ⁴⁵/₄
D. -³/₄

Question 35:

• JAMB 2007

A binary operation Δ is defined by aΔb = a + b + 1 for any numbers a and b. Find the inverse of the real number 7 under the operation Δ, if the identity element is -1

A. -7
B. -9
C. 5
D. 9