Answer :

To determine the Highest Common Factor (HCF) of the expressions [tex]\(9(x + y)\)[/tex] and [tex]\(3(x^2 - y^2)\)[/tex], let's follow these steps:

1. Factorize Each Expression:
- Expression 1: [tex]\(9(x + y)\)[/tex]

This expression is already in its simplest factorized form.

- Expression 2: [tex]\(3(x^2 - y^2)\)[/tex]

Notice that [tex]\(x^2 - y^2\)[/tex] is a difference of squares, which can be factored as [tex]\((x - y)(x + y)\)[/tex]. Therefore:

[tex]\[ 3(x^2 - y^2) = 3(x - y)(x + y) \][/tex]

2. Identify Common Factors:
- From the factorized forms, we have:
[tex]\[ 9(x + y) = 9 \cdot (x + y) \][/tex]
[tex]\[ 3(x^2 - y^2) = 3 \cdot (x - y) \cdot (x + y) \][/tex]

- We see that both expressions share a common factor of [tex]\((x + y)\)[/tex] and a numerical factor related to their coefficients.

3. Determine Numerical HCF of Coefficients:
- The coefficients in the expressions are 9 and 3.
- The HCF of 9 and 3 is 3.

4. Combine the Common Factors:
- Combine the numerical HCF with the common algebraic factor:
[tex]\[ 3 \cdot (x + y) \][/tex]

Therefore, the HCF of [tex]\(9(x+y)\)[/tex] and [tex]\(3(x^2 - y^2)\)[/tex] is:

[tex]\[ 3(x + y) \][/tex]