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
Correct Answer: Option D
Explanation
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