Dwa krótkie zadanka ciągów. Jeśli można to proszę o obliczenia.

1 [latex]a_{7}=2a_{5}\ a_{5}cdot q^2=2a_{5}\ q^2=2\ q=sqrt{2}\ \ Odp: C[/latex] 2 [latex]a_{6}=a_{3}+3r\ 9=24+3r\ 3r=-15\ r=-5\ \ a_{3}=a_{1}+2r\ 24=a_{1}+2cdot (-5)\ 24=a_{1}-10\ a_{1}=34\ \ S_{n}=frac{2a_{1}+(n-1)r}{2}cdot n\ \ S_{4}=frac{2a_{1}+3r}{2}cdot 4=frac{2cdot 34+3cdot (-5)}{2}cdot 4 = (68-15)cdot 2 = 106[/latex]