Answer: b. 195,312
Step-by-step explanation:
[tex]\sum\limits_{i=1}^8-3*(-5)^{i-1}.\\[/tex]
Let's solve using a geometric progression:
[tex]b_1=-3\ \ \ \ q=-5\ \ \ \ S_8=?\\[/tex]
The formula for the sum of a geometric progression
[tex]\displaystyle\\\boxed {S_n=b_1*\frac{q^n-1}{q-1} }[/tex]
[tex]\dIsplaystyle\\\\S_8=-3*\frac{(-5)^8-1}{-5-1}\\\\S_8=\frac{-3*390625}{-6}\\\\S_8=\frac{390625-1}{2}\\ \\S_8=\frac{390624}{2}\\\\S_8=195312.[/tex]
