The task is to determine which of the given sequences are arithmetic sequences. An arithmetic sequence has a constant difference between consecutive terms. Let's analyze each sequence:

1. 100, 200, 400, 800, ...

   • The differences are: $200 - 100 = 100$, $400 - 200 = 200$, $800 - 400 = 400$.
   • The differences are not constant, so this is not an arithmetic sequence.

2. 25, 30, 35, 40, ...

   • The differences are: $30 - 25 = 5$, $35 - 30 = 5$, $40 - 35 = 5$.
   • The differences are constant, so this is an arithmetic sequence.

3. -3, 1, 5, 9, ...

   • The differences are: $1 - (-3) = 4$, $5 - 1 = 4$, $9 - 5 = 4$.
   • The differences are constant, so this is an arithmetic sequence.

4. -4, -12, -36, -108, ...

   • The differences are: $-12 - (-4) = -8$, $-36 - (-12) = -24$, $-108 - (-36) = -72$.
   • The differences are not constant, so this is not an arithmetic sequence.

Conclusion:

The sequences that represent arithmetic sequences are:

• 25, 30, 35, 40, ...
• -3, 1, 5, 9, ...

Would you like further details or have any questions?

Here are 5 relative questions for further exploration:

1. What is the formula to find the nth term of an arithmetic sequence?
2. How do geometric sequences differ from arithmetic sequences?
3. Can a sequence have both arithmetic and geometric properties?
4. What is the sum of the first n terms in an arithmetic sequence?
5. How can we identify a sequence from its general term formula?

Tip: In arithmetic sequences, if you suspect the sequence might be arithmetic, always check the difference between consecutive terms to verify it.