Sorry for taking so long, i have had electricity issues
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To find the sum to n terms for a sequence such as this i have been using sigma notation.
My current workings;
100 + 108 + 116 +... to n/2 terms, -(2^2+4^2+6^2+...) to n/2 terms
(8n+92) -(2n)^2
8(n/2 sigma r=1)r + (n/2 sigma r=1)92 - 4(n/2 sigma r=1)r^2
n(n+2) + 46n - n(n+2)(n+1)/6
Substituting a values for n into this equation is not giving me the sum to n terms. Hence i have done something wrong up to this point.
If you cannot understand anything please ask.