Question

In a geometric sequence, if a2=162 and a5=-6, what is the value of r??

Answer 1

a5/a2 = r^3
hence r^3= -6/162
or r^3= -1/27
or r^3=(-1/3)^3
hence r=-1/3

Answer 2

why do you do that?

Answer 3

"a5/a2 = r^3"

Answer 4

omg! i was subtracting instead of dividing T_T!! thanks so much!

Answer 5

see a5= (a1)*(r^4) and a2=(a1)*(r)
then a5/a2 =((a1)*(r^4))/((a1)*(r))=r^4/r=r^3

Answer 6

i get it!
:) ty