(a) Let the letters A and B represent two different amino acids. Write down the sequences of all the possible tripeptides that could be made with just these two amino acids.
(b) What is the formula for calculating the number of different tripeptides that can be formed from two different amino acids ?

Explanation

### Step-by-Step Solution

#### Part (a): Writing Down the Sequences of All Possible Tripeptides

1. **Identify the Amino Acids**: We have two different amino acids represented by the letters A and B.

2. **Understanding Tripeptides**: A tripeptide consists of three amino acids. Since we can use A and B, we will create sequences of three letters using these two amino acids.

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