Question

identify a1 in a geometric series for which s8=42.5 and r=-0.5

Answer 1

the sum of a geo series takes the form:\[\S_n=a_1\frac{1-r^n}{1-r}]
solve for a1

Answer 2

\[S_n=a_1\frac{1-r^n}{1-r}\]

Answer 3

wow, thanks i was searching for that formula

Answer 4

i found it wedge between the memories of the date of the war of the bulge, and nixons impeachment speech