Question

Use sigma notation to represent the sum of the first five terms of the following sequence. -5, -9.-13,

Answer 1

Answer:

$\sum -5-9-13-17-21$ =-65

Step-by-step explanation:

given nos -5,-9,-13,-17,-21

common difference=-4

given series are in arithmetic progression,

$\sum -5-9-13-17-21$=$n\div 2\left \{ a+l \right \}$

 where, n=5 , a=first term=-5 , l=last term=-21

$\sum -5-9-13-17-21$=$5\div 2\left \{ -5-21\right \}$

$\sum -5-9-13-17-21$ =$5\div 2\left \{ -26\right \}$

$\sum -5-9-13-17-21$ =-65     answer