Chapter 7: Problem 13
Explain how it follows from the definition of logarithm that a. \(\log _{b}\left(b^{x}\right)=x\), for all real numbers \(x\). b. \(b^{\log _{b} x}=x\), for all positive real numbers \(x\).
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Chapter 7: Problem 13
Explain how it follows from the definition of logarithm that a. \(\log _{b}\left(b^{x}\right)=x\), for all real numbers \(x\). b. \(b^{\log _{b} x}=x\), for all positive real numbers \(x\).
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Use the definition of logarithm to prove that for any positive real number \(b\) with \(b \neq 1, \log _{b} b=1\).
Let \(A\) be a set of six positive integers each of which is less than 13. Show that there must be two distinct subsets of \(A\) whose elements when added up give the same sum. (For example, if \(A=\\{5,12,10,1,3,4\\}\), then the elements of the subsets \(S_{1}=\\{1,4,10\\}\) and \(S_{2}=\\{5,10\\}\) both add up to 15.)
Let \(A=\\{1,2,3,4,5\\}\) and define a function \(F: \mathscr{P}(A) \rightarrow \mathbf{Z}\) as follows: For all sets \(X\) in \(\mathscr{P}(A)\), \(F(X)=\) \(= \begin{cases}0 & \text { if } X \text { has an even } \\ & \text { number of elements } \\ 1 & \text { if } X \text { has an odd } \\ & \text { number of elements }\end{cases}\) Find the following a. \(F(\\{1,3,4\\})\) b. \(F(b)\) c. \(F(\\{2,3\\})\) d. \(F(\\{2,3,4,5\\})\)
Prove or give a counterexample: If \(f: X \rightarrow Y\) and \(g: Y \rightarrow\) \(X\) are functions such that \(g \circ f=i_{X}\) and \(f \circ g=i_{Y}\), then \(f\) and \(g\) are both one-to-one and onto and \(g=f^{-1}\).
Consider the coding and decoding functions \(E\) and \(D\) defined in Example 7.1.10. a. Find \(E(0110)\) and \(D(111111000111)\). b. Find \(E(1010)\) and \(D(000000111111)\).
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