The second term of a GP is 4, the fifth term is 81, find the seventh term

2 answers

given:
ar = 4
ar^4 = 81
divide the 2nd by the first:
r^3 = 81/4
r = (81/4)^(1/3) = appr 2.7257
????

are you sure it didn't say , the fourth term is 81 ???
It would work out so nicely!
/(op0/