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Why does sum(1/n) diverge but sum(1/n^2) converge?

Sum(1/n) is shown to converge by bracketing the series correctly and then comparing it with a series we know diverges. Sum(1/n^2) can be shown to converge via the integral test (using y=1/x^2), where the...

Answered by MAT tutor
6494 Views

Show that if a^n - 1 is prime then a = 2. If n is not prime, can 2^n-1 be prime?

This question is based on MAT 2015 question 2. This question has already built up the generalized difference of two powers in the buildup. We can apply this to an - 1 to give: an - 1...

Answered by Mark W. MAT tutor
894 Views

What graph can y = cos^2(x^2)/ x^2 have, for x > 0 ?

Right! Analysing the function "y" we can see that the graph should not exist below the "x" axis, since all the elements that form "y" as a function are positive, no matter wh...

Answered by Dorian G. MAT tutor
501 Views

Let a and b be positive integers such that a+b = 20. What is the maximum value that (a^2)b can take?

We need to maximise the value of (a^2)b given that a+b = 20.The first step is to note that we can eliminate b from these equations to give a problem in just one variable. We have b = 20 - a, so (a^2)b = (...

Answered by Donald F. MAT tutor
3750 Views

How many solutions does the equation 2sin^2(x) - 4sin(x) + cos^2(x) + 2 = 0 have in the domain 0<x<2pi

Firstly lets rearrange the equation to get rid of cos^2(x) to make it easier to solve by using the identity sin^2(x)+cos^2(x) = 1. Then we get 2sin^2(x) - 4sin(x) + 1 - sin^2(x) + 2 = sin^2(x) - 4sin(x) +...

Answered by Disha D. MAT tutor
648 Views

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