Question

Pls help and explain tyyy

Answer 1

11) 195312

13) 5461

Explanation:

11)

15÷(-3) = -5

(-75)÷15 = -5

375÷(-75) = -5

It’s clear that the common ratio of this geometric sequence is -5

Then using the sum formula for geometric sequences :

`S_(11)=\left( -3\right) * (1-\left(-5 \right)^(8) )/(1-(-5)) =-(1)/(2)*(1-(-5)^8)=195312`

……………………………………………………

13)

`S_(13)=1* (1-4^(7))/(1-4) =-(1)/(3) *(1-4^(7))=5461`