``6th term:` a_4 = -18, a_7 = 2/3` Find the indicated term of the geometric sequence.

You need to write the following formula such that:

`a_7 = a_6*q`

`a_6 = a_5*q`

`a_5 = a_4*q`

Replace `a_4*q ` for `a_5` , such that:

`a_6 = a_4*q*q => a_6 = a_4*q^2`

Replace `a_4*q^2` for `a_6` such that:

`a_7 = a_4*q^2*q => a_7 = a_4*q^3 => q^3 = (a_7)/(a_4) => q = root(3)((a_7)/(a_4))`

`q = root(3)((2/3)/(-18)) => q = root(3)(-1/27) => q = root(3)(-1/(3^3))`

`q = -1/3`

You may find `a_6` such that:

`a_6 = (a_7)/q => a_6 = (2/3)/(-1/3) => a_6 = -2`

Hence, evaluating `a_6 ` yields `a_6 = -2.`