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# Finding A First Term Of Geometric Series

ALGEBR-YZNUYE

Find the first term $a_1$ of a geometric sequence given the following two consecutive terms $...,-3281250, 16406250, ...$ and sum of the series:

$$\sum_{i=1}^{13}a_i=8544921882$$

A

$51269531292$

B

$42$

C

$210$

D

$28$

E

none of the above