tolong bantu jawab a dan b dong itu sulit banget

u4 = ar^3= 10/9
u6= ar^5=10/81

[tex]a. \: \frac{u6}{u4} = \frac{ {ar}^{5} }{ {ar}^{3} } \frac{ \frac{10}{81} }{ \frac{10}{9} } \\ {r}^{2} = \frac{90}{810} = \frac{9}{81} = \frac{1}{9} \\ r = \frac{1}{3} [/tex]
[tex]b. \: u4 = {ar}^{3} \\ \frac{10}{9} = a \times ( \frac{1}{3}^{3}) \\ \frac{10}{9} = \frac{1}{27} a \\ 9a = 10 \times 27 \\ a = \frac{270}{9} \\ a = 30[/tex]