Identify, in the following expressions, terms which are not constants. Give their numerical coefficients: `xy+4, 13-y^2, 13-y+5y^2, 4p^2 q-3pq^2+5`

Explanation

To solve the problem of identifying terms that are not constants in the given expressions and finding their numerical coefficients, we will go through each expression step by step.

### Step-by-Step Solution:

1. **Expression 1: \( xy + 4 \)**
- Identify the terms: The terms in this expression are \( xy \) and \( 4 \).
- Determine which term is not a constant: The term \( xy \) is not a constant, while \( 4 \) is a constant.
- Find the numerical coefficient of \( xy \): The coefficient of \( xy \) is \( 1 \) (since \( xy \) can be written as \( 1 \cdot xy \)).
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