The problem asks for the number of five-digit numbers that can be formed without any restrictions. Let's break down the requirements of a five-digit number:
We will calculate the number of such five-digit numbers step-by-step:
The formula used here is:
| Total number of five-digit numbers | = | Number of choices for the first digit × Number of choices for each of the other four digits |
| = | \(9 \times 10 \times 10 \times 10 \times 10\) |
Calculating this, we get:
Thus, the correct answer is 90000.
Option 3 (90000) is the correct answer, as it matches our calculated result. Other options either provide the incorrect number of total possibilities or are not plausible given the constraints.
Given, the function \( f(x) = \frac{a^x + a^{-x}}{2} \) (\( a > 2 \)), then \( f(x+y) + f(x-y) \) is equal to