The 3rd and 5th term of a g.p is 9 and 16.find the 4th term

Answer 1

ar^2 = 9
ar^4 = 16
divide them:
r^2 = 16/9
r = ± 4/3

then a(16/9) = 9
a = 81/16

term(4) = ar^3 = (81/16)(±4/3)^3 = ± 12

or , in a simple way ....
once we have r, just multiply by term(3) to get to term(4)
9*(±4/3) = ±12