Solution:
Concept:
We will first have to calculate the common ratio of the sequence and see the sequence that gives a common ratio of 1/2
From the first option
The formula given in the question is given below as
![\begin{gathered} f(x+1)=(1)/(2)f(x) \\ (f(x+1))/(f(x))=(1)/(2) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/tuj6lh1kaiyf5x9al4gu7hbadsoglbkd2b.png)
From the first option,
![\begin{gathered} r=(T_2)/(T_1)=((x)/(2))/(x)=(1)/(2) \\ r=(T_3)/(T_2)=((x)/(4))/((x)/(2))=(x)/(4)*(2)/(x)=(1)/(2) \\ r=(T_4)/(T_3)=((x)/(6))/((x)/(4))=(x)/(6)*(4)/(x)=(2)/(3)(wrong) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/fqzpmacqm2v5ftrthjgeqmp12se2iguzxq.png)
Hence,
The first option is wrong
From the second option,
![\begin{gathered} r=(T_2)/(T_1)=(2x)/(x)=2 \\ r=(T_3)/(T_2)=(4x)/(2x)=2 \\ r=(T_4)/(T_3)=(8x)/(4x)=2(\text{wrong)} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/zd98hmliv3t3qqnhlentp9o0zwz7xw0php.png)
Hence,
The second option is wrong
From the third option,
![\begin{gathered} r=(T_2)/(T_1)=((x)/(2))/(x)=(1)/(2) \\ r=(T_3)/(T_2)=((x)/(4))/((x)/(2))=(x)/(4)*(2)/(x)=(1)/(2) \\ r=(T_4)/(T_3)=((x)/(8))/((x)/(4))=(x)/(8)*(4)/(x)=(1)/(2)(correct) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/o2cqg71eb2hqbswee3vk4jiz5nwberqtbt.png)
Hence,
The right answer is the third option
![x,(x)/(2),(x)/(4),(x)/(8)](https://img.qammunity.org/2023/formulas/mathematics/college/w91i64tjowi205sq3rxa7o3t5j1ipnysh1.png)