How many 5-digit prime numbers can be formed using the digits 1, 2, 3, 4, 5 if the repetition of digits is not allowed?

If f(x + 1) = x² - 3x + 2, then what is f(x) equal to?

If x², x, -8 are in AP, then which one of the following is correct?

The third term of a GP is 3. What is the product of its first five terms?