Verified answer

Resposta:

[tex]\bold{S_{9} =-1197}[/tex]

Explicação passo a passo:

[tex]a_{1} =(-7)\\\\a_{2} =14\\\\q=\frac{a_{2} }{a_{1} } =\frac{14}{-7} =(-2)\\\\n=9[/tex]

[tex]Fo\´rmula:\ S_{n} =\frac{a_{1} \times (q^{n}-1 )}{q-1}[/tex]

[tex]S_{9} =\frac{(-7) \times ((-2)^{9}-1 )}{-2-1}\\\\S_{9} =\frac{(-7) \times ((-512)-1 )}{-3}\\\\S_{9} =\frac{(-7) \times (-513 )}{-3}\\\\S_{9} =-\frac{3591}{3}\\\\\bold{S_{9} =-1197}[/tex]