geometric progression

Question

the 8th term of a geometric progression[G] is -7/32. find it common ratio if its first term is 28

Answer 1

-1/2 is the common ratio

a1=28

a8=-7/32

an=a1(r^(n-1))

a8 = a1(r^7)

-7/32 =28r^7

r^7 = -7/32/28 = -7/(32)(28)

r = 7th root of (-7/(32)(28))

= -1/2= -0.5= common ratio

a calculator helps

check the answer

a1=28

a2 = -14

a3 =7

a4 =-7/2

a5= 7/4

a6 =-7/8

a7 =7/16

a8 = -7/32