JAMB Mathematics 2007 Objective — Question 20

Question 20 of 50 from the Joint Admissions and Matriculation Board (JAMB) Mathematics 2007 Objective paper, with the correct answer and a full explanation.

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

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

Explanation

Combining an element with its inverse gives the identity: 7+l+1=-1, so l=-1-8=-9.

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