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Help on question about sequences and series watch

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    Write down the term indicated in square brackets in each of the following arithmetic progressions

    81, 77, 73, ... [nth term]


    I did:
    a=81, d=4
    nth term = a+(n-1)d
    81+(n-1)4 = 81+4n-4 = 73+4n


    The answer is 85-4n


    So somwhere I have gone wrong with the signs.
    I'm not sure where though, as far as I can see i've done it all correct, evidentely not.
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    Your "nth term = ..." bit is wrong. Surely it's just nth term = a-nd?
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    u_1 = 81

    u_2 = 77

    u_3 = 73

    so u_n = 81 - 4(n - 1)
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    d=-4 my dear!
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    (Original post by elitespawn)
    d=-4 my dear!
    Got it! Why didn't I see that before? :shy2: Thankyou
 
 
 
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Updated: January 29, 2010
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