V geometrickej postupnosti \( \left\{a_{n}\right\}_{n=1}^{\infty} \) platí: \( a_{1}+a_{3}=15, a_{2}+a_{4}=20 \). Určte \( a_{1} \) a \( q \).
\( q=\frac{4}{3}, a_{1}=\frac{27}{5}=5,4 \)
\( q=\frac{2}{3}, a_{1}=\frac{24}{5}=4,8 \)
\( q=\frac{5}{4}, a_{1}=\frac{30}{5}=6 \)
\( q=\frac{3}{2}, a_{1}=\frac{25}{5}=5 \)
