Question 601673
<pre>
These are the things you need to know to do this problem:

{{{sum(i,i-1,n)}}} = {{{n(n+1)/2}}}

{{{sum(1,i=1,n)}}} = n

{{{sum(k*f(i),i=1,n)}}} = {{{k*sum(f(i),i=1,n)}}}

{{{sum((f(i)+g(i)),i=1,n)}}} = {{{sum(f(i),i=1,n)}}} + {{{sum(g(i),i=1,n)}}}

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{{{sum((6+4i),i=1,81)}}} = {{{sum((6),i=1,81)}}} + {{{sum((4i),i=1,81)}}} = {{{6*sum((1),i=1,81)}}} + {{{4*sum((i),i=1,81)}}} =

{{{6*81}}} + 4·{{{(81*(81+1))/2}}} = 486 + 4·{{{(81*82)/2}}} = 486 + 13284 = 13770

Edwin</pre>