Identify the operations (addition, subtraction, division, multiplication) in forming the following expressions and tell how the expressions have been formed.
`z+1, z - 1, y + 17, y - 17`

Answer

To solve the problem, we will identify the operations used in forming each expression and explain how they were formed step by step.

### Step-by-Step Solution:

1. **Expression: z + 1**
- **Operation:** Addition
- **Formation Explanation:** The expression is formed by taking the variable \( z \) and adding \( 1 \) to it. This can be stated as "1 is added to \( z \)."

2. **Expression: z - 1**
- **Operation:** Subtraction
- **Formation Explanation:** The expression is formed by taking the variable \( z \) and subtracting \( 1 \) from it. This can be stated as "\( 1 \) is subtracted from \( z \)."

3. **Expression: y + 17**
- **Operation:** Addition
- **Formation Explanation:** The expression is formed by taking the variable \( y \) and adding \( 17 \) to it. This can be stated as "17 is added to \( y \)."

4. **Expression: y - 17**
- **Operation:** Subtraction
- **Formation Explanation:** The expression is formed by taking the variable \( y \) and subtracting \( 17 \) from it. This can be stated as "17 is subtracted from \( y \)."

### Summary of Operations:
- **z + 1:** Addition (1 is added to z)
- **z - 1:** Subtraction (1 is subtracted from z)
- **y + 17:** Addition (17 is added to y)
- **y - 17:** Subtraction (17 is subtracted from y)