Sum of the numbers, considering the correct significant figures:
\[ \text{Sum} = 4.6 + 4.6 + 4.632 + 4.64 = 18.4 \]
The arithmetic mean is:
\[ \text{Arithmetic Mean} = \frac{\text{Sum}}{\text{Number of Observations}} = \frac{18.4}{4} = 4.6 \, s \]
The result is rounded to the correct significant figure.
Let $ P_n = \alpha^n + \beta^n $, $ n \in \mathbb{N} $. If $ P_{10} = 123,\ P_9 = 76,\ P_8 = 47 $ and $ P_1 = 1 $, then the quadratic equation having roots $ \alpha $ and $ \frac{1}{\beta} $ is: