Question

Evaluate the expression below

Answer 1

Answer: b. 195,312

Explanation:

`\sum\limits_(i=1)^8-3*(-5)^(i-1).\\`

Let's solve using a geometric progression:

`b_1=-3\ \ \ \ q=-5\ \ \ \ S_8=?\\`

The formula for the sum of a geometric progression

`\displaystyle\\\boxed {S_n=b_1*(q^n-1)/(q-1) }`

`\dIsplaystyle\\\\S_8=-3*((-5)^8-1)/(-5-1)\\\\S_8=(-3*390625)/(-6)\\\\S_8=(390625-1)/(2)\\ \\S_8=(390624)/(2)\\\\S_8=195312.`