Question

a número 1 por gentileza. alguém?

Answer 1

$a_1= \frac{1}{4} \\ a_4=- \frac{2}{27} \\ \\a_n=a_1 \cdot q^{n-1}\\ \\a_4= \frac{1}{4} \cdot q^{4-1}\\ \\- \frac{2}{27}= \frac{1}{4} \cdot q^3\\ \\\frac{1}{4} \cdot q^3=- \frac{2}{27}\\ \\q^3=- \frac{4 \cdot 2}{1 \cdot 27} \\q^3=- \frac{8}{27}\\ \\q= \sqrt[3]{- \frac{8}{27}}\\q=- \frac{2}{3}$