Question

Calcule a soma dos 6 primeiros termos da PG (2,6,18,....)

Answer 1

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$a_1=2 \\ q=6\div2=3 \\ n=6 \\ \\ S_n= \frac{a_1(q^n-1)}{q-1} \\ \\ S_6= \frac{2(3^6-1)}{3-1} \\ \\ S_6= \frac{2(729-1)}{2} \\ \\ S_6= \frac{\not2(728)}{\not2} \\ \\ S_6=728$