Question

ex 32( e,f)
ex 33(a,b)
ex 34
va roggg. sau macar una din ele

Answer 1

34)

$\it y_1=S_1=2\cdot(5-1)=8\\ \\ y_1+y_2=S_2\Rightarrow 8+y_2=2(5^2-1) \Rightarrow 8+y_2=48 \Rightarrow y_2=40\\ \\ q=\dfrac{y_2}{y_1}=\dfrac{40}{8}=5\\ \\ S_4=2(5^4-1)=2\cdot624=1248$