Question

Calcule o quarto e o sétimo termo da P.G (3,-6,12...)

Answer 1

$a_n=a_4=? \\ a_1=3 \\ n=4 \\ q=(-6)\div(3)=-2 \\ \\ termo~~geral \\ \\ a_n=a_1.q^{n-1} \\ \\ a_4=3.(-2)^{4-1} \\ a_4=3.(-2)^3 \\ a_4=3.(-8) \\ a_4=-24 \\ \\ ----------------------- \\ a_n=a_7 \\ a_1=3 \\ n=7 \\ q=-2 \\ \\ a_7=3.(-2)^{7-1} \\ a_7=3.(-2)^6 \\ a_7=3(64) \\ \\ a_7=192$