Discrete Mathematics and Its Applications, Seventh Edition

Published by McGraw-Hill Education
ISBN 10: 0073383090
ISBN 13: 978-0-07338-309-5

Chapter 1 - Section 1.5 - Nested Quantifiers - Exercises - Page 64: 4

Answer

(a) There is a student in your class that has taken a computer science course. (b) There is a student in your class that has taken all computer science courses. (c) All students in your class have taken a computer science course. (d) There is a computer science course that every student in your class has taken. (e) Every computer science course has been taken by some student in your class. (f) All students in your class have taken all computer science courses.

Work Step by Step

Let P(x,y) be the statement "Student x has taken class y," where the domain x is all students, y is computer science classes at your school. (a) There is a student in your class that has taken a computer science course.$$\exists x \exists y P(x,y)$$ (b) There is a student in your class that has taken all computer science courses.$$\exists x \forall y P(x,y)$$ (c) All students in your class have taken a computer science course.$$\forall x \exists y P(x,y)$$ (d) There is a computer science course that every student in your class has taken.$$\exists y \forall x P(x,y)$$ (e) Every computer science course has been taken by some student in your class.$$\forall y \exists x P(x,y)$$ (f) All students in your class have taken all computer science courses.$$\forall x \forall y P(x,y)$$
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