(a)[3]
Calculate the value of $r$.
(b)[2]
Calculate the sum of the first $20$ terms of the geometric progression. Give your answer correct to $4$ significant figures.
(c)[3]
Calculate the sum to infinity of the progression $a_2, a_5, a_8, \ldots$.
Mathematics 9709 · AS & A Level · Series
Series — practice question
For the geometric progression $a_1, a_2, a_3, \ldots$, the first term is $2$ and the common ratio is $r$, where $r > 0$. It is also given that $\frac{2}{9} a_5 + 7a_3 = 8$.