Question

Qual é o 5 termo da p.g (240, -120) ?

Answer 1

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$a_n=a_5=? \\ a_1=240 \\ n=5 \\ q=- \frac{120}{240} =- \frac{1}{2} \\ \\ a_n=a_1.q^{n-1} \\ \\ a_5=240.(- \frac{1}{2} )^{5-1} \\ \\ a_5=240.(- \frac{1}{2} )^4 \\ \\ a_5=240. \frac{1}{16} \\ \\ a_5=15$