Question

b1=-2 q=3/4 Найти: Sn

Answer 1

$Sn = \frac{b1( {q}^{n} - 1) }{q - 1} = \frac{ - 2( {( \frac{3}{4}) }^{n} - 1) }{ \frac{3}{4} - 1 } = \frac{ - 2( \frac{ {3}^{n} }{ {4}^{n} } - 1) }{ - \frac{1}{4} } = 8( \frac{ {3}^{n} }{ {4}^{n} } - 1)$