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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

1273 Views

The actual size of a microrganism is 3.6 micrometres and the image size is 9 cm, what is the magnification of the diagram?

I = A X M M = I / A mm -> μm (x10000) 9 cm = 90000 μm90000 / 3.6 = x 25000 magnification

Answered by Sharon L. • Biology tutor

1872 Views

How would you go about calculating inflation using CPI (consumer price index)

- The consumer price index is the official measure of inflation in the UK - 2 surveys are conducted. The first survey is the Living Costs and Food surveys which involves approx. 7000 household...

Answered by • Economics tutor

1507 Views

b is two thirds of c. 5a = 4c Work out the ratio a : b : c Give your answer in its simplest form where a, b and c are integers

a : c = 4 : 5 and b : c = 2 : 3 so getting a common value of 15 for B gives a : c = 12 : 15 and b : c = 10 : 15 we can now compare these ratios and get 12 : 10 : 15 this is not divisible by any common f...

Answered by jamie c. • Maths tutor

7484 Views

What is the chain rule?

Up until now you may have been given functions like f(x)= 7x^3 +cos(x) and been told just to differentiate. What your teacher really meant was to differentiate with respect to x. The chain rule allows us ...

Answered by James M. • Maths tutor

2592 Views