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Math Help - Help with sums of integers please.

  1. #1
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    Help with sums of integers please.

    Question is:

    i) Find the sum of the integers from 29 to 107 inclusive.

    ii) Hence find the value of

    107
    E (4 + 3i)
    i = 29

    Sorry I don't know how to put in the sigma notation above.

    I can follow what to do until it gets to the part in brackets (4 + 3i), I am not sure why it is that value? It doesn't seem to fit in with the rest of the equation when I have calculated it.

    Thanks in advance.
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  2. #2
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    \sum\limits_{k = 1}^{107} {\left( {4 + 3k} \right)}  = \sum\limits_{k = 1}^{107} {\left( 4 \right)}  + 3\sum\limits_{k = 1}^{107} {\left( k \right)}  = (107)(4) + 3\frac{{\left( {107} \right)\left( {108} \right)}}<br />
{2}
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  3. #3
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    Thanks for replying but unfortunately that has me more confused, why have you swapped i=29 for k=1?
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  4. #4
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    Quote Originally Posted by mrszone View Post
    Thanks for replying but unfortunately that has me more confused, why have you swapped i=29 for k=1?
    To give you a way to solve general questions.
    Here is the general idea: \sum\limits_{k = 29}^{107} {\left( k \right)}  = \sum\limits_{k = 1}^{107} {\left( k \right)}  - \sum\limits_{k = 1}^{28} {\left( k \right)}
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