Question 1085482
<pre>
1)   {{{sum(k,k=1,7)=1+2+3+4+5+6+7=28}}}

Or you can use the formula with n = 7

{{{sum(k,k=1,n)=(n(n+1))/2=(7(7+1))/2=(7(8))/2=56/2=28}}}

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2)   {{{sum(k,k=12,7)=1^2+2^2+3^2+4^2+5^2+6^2+7^2+8^2+9^2+10^2+11^2+12^2}}}{{{""=""}}}

{{{1+4+9+16+25+36+49+64+81+100+121+144=650}}}

Or you can use the formula with n = 12

{{{sum(k^2,k=1,n)=(n(n+1)(2n+1))/6=(12(12+1)(2*12+1))/6=(12(13)(24+1))/6=(12(13)(25))/6=3900/6=650}}}

Edwin</pre>