Question

Va rog frumos e urgent dau corona ex 2 și 4

Answer 1

2). 
$b_{8} = b_{1}* q^{8-1} \\ b_{8}= 3 * (-1) ^{7} \\ b_{8}= 3*(-1)= -3$
4). 
[tex]S_{10} = b_{1} * \frac{q^{10}-1}{q-1}=4 * \frac{ \frac{1}{2^{10}} -1 }{- \frac{1}{2} } = \\ \\ = -2^{2} * \frac{ \frac{1-2^{10}}{2^{10}} }{ \frac{1}{2} } =-2^2* \frac{1-2^{10}}{2^9}= \\ \\ = - \frac{1-2^{10}}{2^7}= - \frac{1-2^{10}}{128} = - \frac{1-1024}{128}= - \frac{-1023}{128} = \\ \\ = \frac{1023}{128} [/tex]