Question

Find the sum of first 6 terms 1,-1/3,1/9,-1/27

Answer 1

Answer:

as from series we can see that it is

G.P(geometrical ratio) in the common ratio is same

a =1

r= G2/G1 = -1/3

n(no. of terms) =6

G5= ar^4 = 1*(-1/3)^4= 81

G6= ar^5 = 1*(-1/3)^5= 243

sum of first 6 terms = a( r^n -1 / r-1 )

= 1*[(-1/3^6-1)/(-1/3-1)]

= -728*3/ 729*(-4)

hope this will help u