Question

Use the geometric mean to find the 7th term in a geometric sequence if the 6th term is 12 and the 8th term is 27. 20 19.5 18 17

Answer 1

a₆ =12

a₇ = ?? = x

a₈ 27

In this case x is the geometric mean & as per the formula
geometric mean of 2 numbers =√(a₆ * a₈) = √(12*27)
& x=18.
Proof:
Find the common ratio between a₇ & a₆ ==> = ( x) / 12
now find the common ration between a₈ & a₇ ===> =27 / (x)
x/12 = 27/x ===> x² = 12*27 ==> x² = 324 & x =√324 = 18