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julieefang

  • 2 years ago

What is the sum of a 22-term arithmetic sequence where the first term is 56 and the last term is -28?

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  1. ghazi
    • 2 years ago
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    \[S _{n}=\frac{ n }{ 2 }[2a+(n-1)d]\]

  2. ghazi
    • 2 years ago
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    or you can use \[S _{n}=\frac{ n }{ 2 } (a _{1}+a _{n})\]

  3. ghazi
    • 2 years ago
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    n=22, a1=56 and an=-28 put the values in, in the second formula and you will have the sum

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