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 66: 14

Answer

a) $\exists$xH(x) b) $\forall$xS(x) c) $\exists$xV(x,'Alaska') $\land$ $\neg$V(x,'Hawai') d) $\forall$x$\exists$yL(x,y) e) $\exists$x$\exists$y$\forall$z(O(y,z)$\rightarrow$T(x,z)) f) $\exists$x$\exists$y(G(x,t) $\land$ G(y,t)) g) $\forall$x$\exists$y$\exists$z(C(x,y,z))

Work Step by Step

The domain x of the problems is all the students in the class. a) $\exists$xH(x), where H(x) is "x can speak Hindi". b) $\forall$xS(x), where S(x) is "x play a sport". c) $\exists$xV(x,'Alaska') $\land$ $\neg$V(x,'Hawai'), where V(x, y) is "x has visited y". d) $\forall$x$\exists$yL(x,y), where L(x,y) is "x has learned programming language y", the domain for y is all the countries in the world. e) $\exists$x$\exists$y$\forall$z(O(y,z)$\rightarrow$T(x,z)), where O(y,z) is "Department y offer course z", T(x,z) is "Student x has taken course z", the domain for y is all the departments in the school, the domain of z is all the courses in the school. f) $\exists$x$\exists$y(G(x,t) $\land$ G(y,t)), where G(x,t) is "x grew up in town t", the domain for y is all the students in the class, the domain for t is all the towns in the world. g) $\forall$x$\exists$y$\exists$z(C(x,y,z)), where C(x,y,z) is "Student x has chatted with student y in group z", the domain of y is all the students in the class, the domain of z is all the chat groups formed by the students.
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