JAMB - Mathematics (2006 - No. 36)
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
1/12
10/3
1/20
9/5
Explicació
x ⊕ y = xy/6 = xe/6 = x
xe = 6x
e = 6
x ⊕ y = xx1/6 where x1 = 20
x x 20/6 = 6
x = 36/20
x = 9/5
xe = 6x
e = 6
x ⊕ y = xx1/6 where x1 = 20
x x 20/6 = 6
x = 36/20
x = 9/5