题目
Problem
The first term of a convergent geometric progression is 10. The sum of the first 4 terms of the progression is and the sum of the first 8 terms of the progression is . It is given that .
Find the two possible values of the sum to infinity.
[5]
题目中文翻译
一个收敛等比数列的首项为 10。该数列前 4 项的和为 ，前 8 项的和为 。已知 。
求无穷和的两个可能值。