Let the first three terms of a G.P. be $\frac{a}{r}, a, a r$.
Product of three terms $=\frac{a}{r} \times a \times a r=1$
$\therefore a^3=1 \Rightarrow a=1$
Sum of these term $\frac{1}{r}+1+r=\frac{39}{10} \quad$ (put $a=1$ )
Multiplying by $10 r ; 10+10 r+10 r^2=39 r$
$\begin{aligned}
&\Rightarrow 10 r^2+10 r-39 r+10=0 \\
&\Rightarrow 10 r^2-29 r+10=0 \\
&\Rightarrow(2 r-5)(5 r-2)=0 \Rightarrow r=\frac{5}{2} \text { or } \frac{2}{5}
\end{aligned}$
When $r=\frac{5}{2}$ the terms of G.P. are $\frac{2}{5}, 1, \frac{5}{2}$
When $r=\frac{2}{5}$, the terms of G.P. are $\frac{5}{2}, 1, \frac{2}{5}$