Question 312125
In the formula, substitute the value for n and simplify,
{{{S(n)=(n(n+1)(2n+1))/6}}}
When n=1,
{{{S(1)=(1(1+1)(2(1)+1))/6 }}}
{{{S(1)=((1)(2)(3))/6=6/6=1}}}
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When n=2,
{{{S(2)=(2(2+1)(2(2)+1))/6}}}
{{{S(2)=(2(3)(5))/6=30/6=5}}}
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When n=3,
{{{S(3)=(3(3+1)(2(3)+1))/6}}}
{{{s(3)=(2(4)(7))=56/6=28/3}}}
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There it is for 3 problems.
Try and complete the remainng two in a similar fashion.
Repost if you get stuck.