Question 367815
81+27+9+3....=81(1+1/3+1/9+1/27+...)
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{{{S/81=1+sum((1/3)^i,i=1,infinity)}}}
{{{S/81=1+(1/3)/(1-(1/3))}}}
{{{S/81=1+(1/3)/(2/3)}}}
{{{S/81=1+1/2}}}
{{{S/81=3/2}}}
{{{highlight(S=243/2)}}}