sum of a geometric sequence for a1=first term and n=which one and r is common ratio is [tex]S_n= \frac{a_1(1-r^n)}{1-r} [/tex] so a1=1 students r=4 n=5 [tex]S_n= \frac{1(1-4^5)}{1-4} [/tex] [tex]S_n= \frac{(1-1024)}{-3} [/tex] [tex]S_n= \frac{-1023}{-3} [/tex] 314 people know