A G.P has 6 terms. If the 3rd and 4th term are 28 and -56 respectively find common ratio, first term and the sum of the G.P.

Answer 1

from the given:
term(3) = ar^2 = 28
term(4) = ar^3 = -56

so ar^3/(ar^2) = -56/28
r = -2

then in ar^2 = 28
a(4) = 28
a = 7

sum(6) = a(r^6 - 1)/(r-1)
= 7((-2)^6 - 1)/(-2-1)
= 7(63/-3) = -147

check:
GP is 7, -14 , 28 , - 56 , 112, - 224
sum of that is -147

Answer 2

Why are you divide 24 in 8

Answer 3

help to resolve

Answer 4

the 8 terms of gp is 640 and the first terms is 5 find the common ration and 10 terms

Answer 5

Not what i asked was given

Answer 6

Bad