An operation * is defined on the set of real numbers by a*b = a + b + 1. If the identity elements is -1, find the inverse of the element 2 under *.
A
4
B
zero
C
-2
D
-4
Verified Correct Answer: D.
Step-by-Step Mathematical Solution
By definition a*b = a + b + 1.
Let the inverse of the element 2 be x,
Therefore 2*x = -1
i.e. 2 + x + 1 = -1
3 + x = -1
x = -1 - 3
x = -4
Source: Myschool Past Questions Archive (Record #1152)