$\begin{aligned}
& a_1 a_5=28 \Rightarrow a^2 r^4=28 \
& a_2+a_4=29 \Rightarrow a r+a r^3=29
\end{aligned}aranda r^3arerootsof\begin{aligned}
& k^2-29 k+28=0 \
& \Rightarrow \quad k=1, k=28 \
& a r=1, a r^3=28 \
& r^2=28, a^2=\frac{1}{28} \
& a_6=a r^5 \Rightarrow r^4=28^2 \
& \Rightarrow a_6=784
\end{aligned}$