Question

urgent! va rog! dau coroana

Answer 1

Determinăm rația progresiei geometrice:

$\it q=\dfrac{b_2}{b_1}=\dfrac{-2}{1}=-2\\ \\ S_5=b_1\dfrac{q^5-1}{q-1}=1\cdot\dfrac{(-2)^5-1}{-2-1}=\dfrac{-32-1}{-3}=\dfrac{-33}{-3}=11$