Question

Encontre o 12 termo da P.G.( 243/256,81/128,...)

Answer 1

$a_1=\dfrac{243}{256}\\r=\dfrac{81}{128}-\dfrac{243}{256}=\dfrac{162-243}{256}=\boxed{-\dfrac{81}{256}}\\n=12\\a_n=a_1+(n-1)\times r\\a_{12}=\dfrac{243}{256}+(12-1)\times \left(-\dfrac{81}{256}\right)\\a_{12}=\dfrac{243}{256}+11\times \left(-\dfrac{81}{256}\right)\\a_{12}=\dfrac{243}{256}-\left(\dfrac{11\times 81}{256}\right)\\a_{12}=\dfrac{243}{256}-\dfrac{891}{256}\right)\\a_{12}=-\dfrac{648}{256}=-\dfrac{162}{64}=\boxed{-\dfrac{81}{32}}\to \text{12\º termo}$

Espero ter sido útil