Answer:
Proved
Step-by-step explanation:
The given data is:
[tex]11^n - 6[/tex] not [tex]11^{n - 6[/tex]
Required
Prove by induction that it is divisible by 5
Assume [tex]n = k[/tex]
So, we have:
[tex]11^k - 6 = 5p[/tex] where p is a positive digit
Rewrite as:
[tex]11^k = 5p + 6[/tex]
To solve further, we have to prove that [tex]11^k - 6[/tex] is true for [tex]n=k+1[/tex]
So, we have:
[tex]11^{k+1} - 6[/tex]
[tex]11^{k+1} - 6 = 11^k * 11 - 6[/tex]
Add 0
[tex]11^{k+1} - 6 = 11^k * 11 - 6 + 0[/tex]
Replace 0 with [tex]-5 +5[/tex]
[tex]11^{k+1} - 6 = 11^k * 11 - 6 - 5 + 5[/tex]
[tex]11^{k+1} - 6 = 11^k * 11 - 11- 5[/tex]
Factorize
[tex]11^{k+1} - 6 = 11 (11^k - 1)- 5[/tex]
Substitute [tex]11^k = 5p + 6[/tex]
[tex]11^{k+1} - 6 = 11 (5p + 6- 1)- 5[/tex]
[tex]11^{k+1} - 6 = 11 (5p + 5)- 5[/tex]
Factorize
[tex]11^{k+1} - 6 = 11 *5(p + 1)- 5[/tex]
Factorize
[tex]11^{k+1} - 6 = 5[11(p + 1)- 1][/tex]
The 5 outside the bracket implies that it is divisible by 5
