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An operation * is defined on the set of real numbers by a * b...

Mathematics
JAMB 2005

An operation * is defined on the set of real numbers by a * b = ab + 2(a + b + 1). find the identity element

  • A. 2
  • B. 1
  • C. -1
  • D. -2
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Correct Answer: Option C
Explanation

a * b = ab + 2(a + b + 1)
let e be the identity element
∴ a * e = e * a = a
∴ a * e = a
ae + 2(a + e + 1) = a
ae + 2a + 2e + 2 = a
ae + 2e = a - 2a = 2
(a + 2)e = -a - 2
e = -a-2 / (a+2)
e = -(a+2) / (a+2)
e = -1


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Project Topics and Materials, Post-UTME past questions - Download now or upload yours to get paid
NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
Join your school's WhatsApp group
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789
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Project Topics and Materials, Post-UTME past questions - Download now or upload yours to get paid