Prove that 27(23^n)+17(10^2n)+22n is divisible by 11 for n belongs to the natural numbers

Proofs come in many shapes and sizes but this one is done via induction. When doing proof by induction, examiners love a list of a clear definite list of steps, the first being the base case, in this case it's n=1 (as n belongs to the natural numbers) so, 27(231)+17(1021)+221 = 27(23)+17(100)+22 = 621+1700+22 = 2343 (which when divided by 11 gives 213, a lovely whole number! therefore the base case has been proved true) Now that we've finished with with showing the base case true we can jump into the meat and bones of this proof. We're going to "Assume n=k true." so, "27(23k)+17(102k)+22k = 11Z" where Z is a whole number. Next, let's consider the case of n=k+1 then, "27(23k+1)+17(102(k+1))+22(k+1)" = "2723k+27231+17102k+17102+22k+221" Let's group up these terms, so "27231+17102+221" is actually what we did in our base-case, it's 2343 (which is divisible by 11), next we have our "2723k+17102k+22k" does this look familiar? It's because it's our assumption! So, by using our assumption we can see that "2723k+17102k+22k" = 11Z and therefore, "2343+11Z=11(213+Z)", and for the finale the finishing sentence "We have shown that if it is true for n=k then it's true for n=k+1 since we've shown true for n=1 it must be true for all natural numbers"

Answered by Further Mathematics tutor

2169 Views

See similar Further Mathematics A Level tutors

Related Further Mathematics A Level answers

All answers ▸

Given a curve with parametric equations, x=acos^3(t) and y=asin^3(t), find the length of the curve between points A and B, where t=0 and t=2pi respectively.


The finite region bounded by the x-axis, the curve with equation y = 2e^2x , the y-axis and the line x = 1 is rotated through one complete revolution about the x-axis to form a uniform solid. Show that the volume of the solid is 2π(e^2 – 1)


Given that the equation x^2 - 2x + 2 = 0 has roots A and B, find the values A + B, and A * B.


Prove, by induction, that 4^(n+1) + 5^(2n-1) is always divisible by 21


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences