Discrete Mathematics and Its Applications, Seventh Edition

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

Chapter 5 - Section 5.1 - Mathematical Induction - Exercises - Page 330: 9

Answer

a) 2+4+6+.... +2n=n (n+1) b) BASIC STEP: it is given that the n is positive integer then, put n=1 2=n (n+1) = 1 (1+1) =2 (The left-hand side of this equation is 2 because 2 is the sum of the first a positive integer. The right-hand side is found by substituting 2 for n in n (n+1)). INDUCTIVE STEP: For the inductive hypothesis we assume that P(k) 2+4+6+…. +2k=k (k+1) Under the assumption, it must be show that P(k+1) is true, namely, that. 2+4+6… +2(k+1) =(k+1) (k+2) When we add 2(k+1) to both side of the equation in P(K), we obtain. 2+4+6+… +2k+2(k+1) = k (k+1) +2(k+1) [By the inductive hypothesis] = (k+1) (k+2) We have completed the basis step and the inductive step, so by mathematical inductive we know that P(n) is true for all positive integers n. That is, we have proven that. 2+4+6+.... +2n=n (n+1)

Work Step by Step

a) 2+4+6+.... +2n=n (n+1) b) BASIC STEP: it is given that the n is positive integer then, put n=1 2=n (n+1) = 1 (1+1) =2 (The left-hand side of this equation is 2 because 2 is the sum of the first a positive integer. The right-hand side is found by substituting 2 for n in n (n+1) ). INDUCTIVE STEP: For the inductive hypothesis we assume that P(k) 2+4+6+…. +2k=k (k+1) Under the assumption, it must be show that P(k+1) is true, namely, that 2+4+6… +2(k+1)=(k+1) (k+2) When we add 2(k+1) to both side of the equation in P(K), we obtain 2+4+6+… +2k+2(k+1) = k (k+1)+2(k+1) [By the inductive hypothesis] = (k+1)(k+2) We have completed the basis step and the inductive step, so by mathematical inductive we know that P(n) is true for all positive integers n. That is, we have proven that. 2+4+6+.... +2n=n (n+1)
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