13 + 33 + 53 + --- --- + (2n – 1)3 = n²(2n² – 1) |

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter2: Equations And Inequalities
Section2.1: Equations
Problem 5E
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Use mathematical induction to prove the follwing formulae for every positive integer n 

1^3+ 3^3+5^3+.......+(2n-1)^3=n^2 (2n^2-1)

I am trying to understand the concept of n=k+1 and showing that this concept is true.

I have also attached where I am in trying to understand this concept for ease of reference.

13 + 33 + 53 +
+ (2n – 1)3 = n²(2n² – 1)
Show that P (1) is true
Let n= 1
13 = 12(2(1)² – 1)
13 = 12(2 – 1)
13 = 12(1)
13 = 13
Therefore, the result is true for n=1
Assume P(k) is true, therefore let n = k
13 + 33 + 53 ±-
+ (2k – 1)3 = k²(2k² – 1)
Show that n = k +1 is true
13 + 33 + 53 + ---+(2k – 1)³ + 2k³ = (k + 1)² (2(k + 1)² – 1)
k²(2k² – 1) + 2k³ = (k + 1)² (2(k² + 2k)
2k4 – k2 + 2k3 = (k² + 2k + 1)(2k² + 4k)
Transcribed Image Text:13 + 33 + 53 + + (2n – 1)3 = n²(2n² – 1) Show that P (1) is true Let n= 1 13 = 12(2(1)² – 1) 13 = 12(2 – 1) 13 = 12(1) 13 = 13 Therefore, the result is true for n=1 Assume P(k) is true, therefore let n = k 13 + 33 + 53 ±- + (2k – 1)3 = k²(2k² – 1) Show that n = k +1 is true 13 + 33 + 53 + ---+(2k – 1)³ + 2k³ = (k + 1)² (2(k + 1)² – 1) k²(2k² – 1) + 2k³ = (k + 1)² (2(k² + 2k) 2k4 – k2 + 2k3 = (k² + 2k + 1)(2k² + 4k)
13 + 33 + 53 +-
+ (2n – 1)3 = n²(2n² – 1)
Transcribed Image Text:13 + 33 + 53 +- + (2n – 1)3 = n²(2n² – 1)
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