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
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
mΔn = m+n+mn
Let e be the identity element
∴mΔe = eΔm = m
m+e+me = m
e+me = m-m
e+me = 0
e(1+m) = 0
e = 0 / (1+m)
e = 0
Source: Myschool Past Questions Archive (Record #9277)