1. **Problem Statement:**
Given a geometric progression (GP) with the first term $a_1 = 108$ and the fifth term $a_5 = \frac{4}{3}$, find:
(i) The two possible values of the common ratio $r$.
(ii) The corresponding values of the 2nd, 3rd, and 4th terms.
2. **Formula and Rules:**
In a GP, the $n$th term is given by:
$$a_n = a_1 \times r^{n-1}$$
where $a_1$ is the first term and $r$ is the common ratio.
3. **Find the common ratio $r$:**
Given $a_5 = \frac{4}{3}$, substitute $n=5$:
$$\frac{4}{3} = 108 \times r^{4}$$
Divide both sides by 108:
$$r^{4} = \frac{4}{3} \div 108 = \frac{4}{3} \times \frac{1}{108} = \frac{4}{324} = \frac{1}{81}$$
4. **Solve for $r$:**
$$r^{4} = \frac{1}{81}$$
Since $81 = 3^4$, we have:
$$r^{4} = \left(\frac{1}{3}\right)^4$$
Taking the fourth root:
$$r = \pm \frac{1}{3}$$
5. **Find the unknown terms for each $r$:**
- For $r = \frac{1}{3}$:
$$a_2 = 108 \times \frac{1}{3} = 36$$
$$a_3 = 108 \times \left(\frac{1}{3}\right)^2 = 108 \times \frac{1}{9} = 12$$
$$a_4 = 108 \times \left(\frac{1}{3}\right)^3 = 108 \times \frac{1}{27} = 4$$
- For $r = -\frac{1}{3}$:
$$a_2 = 108 \times \left(-\frac{1}{3}\right) = -36$$
$$a_3 = 108 \times \left(-\frac{1}{3}\right)^2 = 108 \times \frac{1}{9} = 12$$
$$a_4 = 108 \times \left(-\frac{1}{3}\right)^3 = 108 \times \left(-\frac{1}{27}\right) = -4$$
**Final answers:**
- Common ratios: $r = \frac{1}{3}$ or $r = -\frac{1}{3}$
- Corresponding terms:
- For $r=\frac{1}{3}$: $36, 12, 4$
- For $r=-\frac{1}{3}$: $-36, 12, -4$
Gp Common Ratio 5D639D
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