Question 398083
sum of the n numbers in a geometric progression
{{{S=(a(r^n-1))/(r-1)}}}
a=2, r=2
S=254
{{{(2(2^n-1))/(2-1)=254}}}
{{{2^n-1=127}}}
{{{2^n=128}}}
{{{2^n=2^7}}}
{{{n=7}}}