Discrete Mathematics with Applications 4th Edition

Published by Cengage Learning
ISBN 10: 0-49539-132-8
ISBN 13: 978-0-49539-132-6

Chapter 3 - The Logic of Quantified Statements - Exercise Set 3.2 - Page 117: 46

Answer

There exists a function that is a polynomial and does not have a real root.

Work Step by Step

Recall the definition of sufficient: "$\forall x$, r(x) is a sufficient condition for s(x)" means "$\forall x$, if r(x) then s(x)." In this case, r(x) is: function is a polynomial. s(x) is: function has a real root. Recall the form of the negation of a universal conditional statement: $~(\forall x, P(x) \rightarrow Q(x)) \equiv \exists x$ such that $(P(x) \land $ ~$Q(x))$ In this case the negation is: "$\exists$ x such that r(x) and ~s(x)" which is, "there exists a function that is a polynomial and does not have a real root."
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