Chapter 11 - 11.3 - Geometric Sequences and Series - 11.3 Exercises - Page 795: 44

$a_1=12$

$a_n=a_1r^{n-1}$ $a_2=a_1r$ $a_5=a_1r^4$ $\frac{a_5}{a_2}=\frac{a_1r^4}{a_1r}$ $\frac{\frac{3}{64}}{3}=r^3$ $r^3=\frac{1}{64}$ $r=\sqrt[3] {\frac{1}{64}}=\frac{1}{4}$ $a_2=a_1r$ $a_1=\frac{a_2}{4}=\frac{3}{\frac{1}{4}}=12$