Question

Na P.G. ( 1/2, - 1, 2, - 4 ), obter a9 e a10.

Answer 1

$> resolucao \\ \\ \geqslant progressao \: geometrica \\ \\ q = \frac{a2}{a1} \\ q = \frac{ - 1}{ \frac{1}{2} } \\ q = - 1 \times \frac{2}{1} \\ q = - \frac{2}{1} \\ q = - 2 \\ \\ \geqslant \: o \: nono \: termo \: da \: pg \\ \\ an = a1 \times q {}^{n - 1} \\ an = \frac{1}{2} \times - 2 {}^{9 - 1} \\ an = \frac{1}{2} \times - 2 {}^{8} \\ an = \frac{1}{2} \times 256 \\ an = \frac{256}{2} \\ an = 128 \\ \\ \\ \geqslant \: o \: decimo \: termo \: da \: pg \\ \\ an = a1 \times q {}^{n - 1} \\ an = \frac{1}{2} \times - 2 {}^{10 - 1} \\ an = \frac{1}{2} \times - 2 {}^{9} \\ an = \frac{1}{2} \times - 512 \\ an = - \frac{512}{2} \\ an = - 256 \\ \\ > < > < > < > < > < > < > < > >$