a) Wyznaczmy iloraz:

$\frac{{a}_{{n}}}{{a}_{{{n}-{1}}}}={q}$ 

${q}=\frac{{\frac{{25}}{{64}}}}{{\frac{{25}}{{32}}}}$ 

${q}=\frac{{25}}{{64}}\cdot\frac{{32}}{{25}}$ 

${q}=\frac{{1}}{{2}}$