4. In a geometric sequence, ag = 64 and a 10 = 0.25.Use the geometric mean to find the value of ag.3216

We are asked to determine the term between the 8th and 10th terms of the geometric sequence. To do that we need to have into account that in a geometric sequence the term between two given terms is equivalent to the geometric mean of the two terms. The geometric terms between the two terms is given by:
[tex]G_m=\sqrt[]{a_1a_2}[/tex]Replacing the values:
[tex]\begin{gathered} G_m=\sqrt[]{(64)(0.25)}_{} \\ G_m=\sqrt[]{16} \\ G_m=4 \end{gathered}[/tex]Therefore, the 9th term is 4.