Classify into monomials, binomials and trinomials.
`ab+bc+ca`

Answer

To classify the expression \( ab + bc + ca \) into monomials, binomials, and trinomials, we can follow these steps:

### Step 1: Understand the Definitions
- **Monomial**: An algebraic expression that contains only one term. For example, \( 3x \) or \( 5ab \).
- **Binomial**: An algebraic expression that contains exactly two terms. For example, \( x + y \) or \( 2a + 3b \).
- **Trinomial**: An algebraic expression that contains exactly three terms. For example, \( x + y + z \) or \( a + b + c \).

### Step 2: Analyze the Given Expression
The expression we have is \( ab + bc + ca \).

### Step 3: Count the Terms
Now, let's count the number of terms in the expression:
1. The first term is \( ab \).
2. The second term is \( bc \).
3. The third term is \( ca \).

### Step 4: Classify the Expression
Since there are three terms in the expression \( ab + bc + ca \), we classify it as a **trinomial**.

### Final Answer
The expression \( ab + bc + ca \) is a **trinomial**.

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