Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 5 - Number Theory and the Real Number System - Chapter Summary, Review, and Test - Review Exercises - Page 335: 79

Answer

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Work Step by Step

(a) The set of all the counting numbers, namely \[1,2,3,\] and so on is called natural number. It is denoted by the letter\[N\]. \[N=\left\{ 1,2,3,4,5,... \right\}\] Consider each element of the provided set: Only \[\sqrt{81}\left( =9 \right)\] is a natural number. Rest \[-17,-\frac{9}{13},0,0.75,\sqrt{2}\text{ and }\pi \] are not natural numbers. Hence, set of natural number from the provided set is,\[\left\{ \sqrt{81} \right\}\]. (b) The set of all the counting numbers along with \[0\], namely \[0,1,2,3,\] and so on is called whole number. It is denoted by the letter\[W\]. \[W=\left\{ 0,1,2,3,4,5,... \right\}\] Consider each element of the provided set: Here, \[0\text{ and }\sqrt{81}\left( =9 \right)\]are whole numbers. Rest \[-17,-\frac{9}{13},0.75,\sqrt{2}\text{ and }\pi \] are not whole numbers. Hence, set of whole number from the provided set is,\[\left\{ 0,\sqrt{81} \right\}\]. (c) The set of all the counting numbers, namely \[1,2,3,\] and so on along with \[0\] and also negative of counting numbers, is called integers. It is denoted by the letter \[Z\]. \[Z=\left\{ ...,-3,-2,-1,0,1,2,3,... \right\}\] Consider each element of the provided set: Here,\[-17,0\text{ and }\sqrt{81}\left( =9 \right)\]are integers. Rest \[-\frac{9}{13},0.75,\sqrt{2}\text{ and }\pi \] are not integers. Hence, set of integers from the provided set is \[\left\{ -17,0,\sqrt{81} \right\}\]. (d) All those numbers that can be represented in the form of \[\frac{p}{q}\], where both \[p\text{ and }q\]are integers and \[q\ne 0\] are called rational number. It is denoted by the letter \[Q\]. \[Q=\left\{ \frac{p}{q}\left| p,q\in Z\And q\ne 0 \right. \right\}\] Consider each element of the provided set: Here,\[-17,-\frac{9}{13},0,0.75\text{ and }\sqrt{81}\left( =9 \right)\]are rational numbers. Rest \[\sqrt{2}\text{ and }\pi \] are not rational numbers. Hence, set of a rational number from the provided set is \[\left\{ -17,-\frac{9}{13},0,0.75,\sqrt{81} \right\}\]. (e) Those numbers that cannot be represented in the form of \[\frac{p}{q}\], where both \[p\text{ and }q\]are integers and \[q\ne 0\] are called irrational number. It is denoted by the letter \[I\]. \[\begin{align} & I=R-Q \\ & =R-\left\{ \frac{p}{q}\left| p,q\in Z\And q\ne 0 \right. \right\} \end{align}\] Where,\[R\] is the set of Real numbers and \[Q\] is the set of Rational numbers. Consider each element of the provided set: Here,\[\sqrt{2}\text{ and }\pi \]are an irrational number. Rest \[-17,-\frac{9}{13},0,0.75\text{ and }\sqrt{81}\] are not irrational numbers. Hence, set of irrational numbers from the provided set is \[\left\{ \sqrt{2},\pi \right\}\]. (f) The set formed by a collection of all rational and irrational numbers are called real number. It is denoted by the letter\[R\]. \[R=Q\cup I\] Where,\[Q\] is the set of all rational numbers and \[I\] is the set of all irrational numbers. Consider each element of the provided set: All the elements of the provided set are real numbers Hence, set of real numbers from the provided set is,\[\left\{ -17,-\frac{9}{13},0,0.75,\sqrt{2},\pi ,\sqrt{81} \right\}\].
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