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    So i started from sub n = 1 and it is = to 5, which is divisible by 5. Then i have done the assumption step. But i am stuck after that, with n = k+1 terms. Can someone help please?
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    Show that f(k+1) - f(k) is also divisible by 5.
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    (Original post by Zacken)
    Show that f(k+1) - f(k) is also divisible by 5.
    im struggling on this question too, cant seem to get a five out of it, any chance you can offer a few more hints
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    (Original post by alesha98)
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    So i started from sub n = 1 and it is = to 5, which is divisible by 5. Then i have done the assumption step. But i am stuck after that, with n = k+1 terms. Can someone help please?
    (Original post by emilyp2206)
    im struggling on this question too, cant seem to get a five out of it, any chance you can offer a few more hints
    When you have powers of two different numbers, it is useful to do f(k+1) - 2 f(k) or f(k+1) - 3 f(k) which makes one of the terms vanish.

    Because this one has 2k in the powers, try f(k+1) - 4f(k).

    It's a nasty question.
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    (Original post by tiny hobbit)
    When you have powers of two different numbers, it is useful to do f(k+1) - 2 f(k) or f(k+1) - 3 f(k) which makes one of the terms vanish.

    Because this one has 2k in the powers, try f(k+1) - 4f(k).

    It's a nasty question.
    i think i may have gone the wrong way about it, ended with 3^2k+1 - 4(3^2k-1)
    and then i ended up in circles
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    (Original post by emilyp2206)
    i think i may have gone the wrong way about it, ended with 3^2k+1 - 4(3^2k-1)
    and then i ended up in circles
    Now take out a common factor of the lowest power of 3, i.e. 3^(2k-1)
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    OHHH multiplying by 4 should mean algebraically you get x + 4x = 5x in the simplest terms right?

    eDIT- this was a different way, or a way that not works at all
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    (Original post by tiny hobbit)
    Now take out a common factor of the lowest power of 3, i.e. 3^(2k-1)
    im grinning, it worked, im happy and thankful
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    http://www.examsolutions.net/maths-r...FP1/module.php

    Go through the mathematical inductions if u havent.Explains every little thing,if its to a power what u do and if its not to a power what u do.
 
 
 
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