Answer :

To express [tex]\((3x + 1)(3x + 3)\)[/tex] as a trinomial, we can use the distributive property, often referred to as the FOIL method (First, Outer, Inner, Last), to expand the product.

1. First Terms:
Multiply the first terms in each binomial:
[tex]\[ 3x \cdot 3x = 9x^2 \][/tex]

2. Outer Terms:
Multiply the outer terms in the expression:
[tex]\[ 3x \cdot 3 = 9x \][/tex]

3. Inner Terms:
Multiply the inner terms in the expression:
[tex]\[ 1 \cdot 3x = 3x \][/tex]

4. Last Terms:
Multiply the last terms in each binomial:
[tex]\[ 1 \cdot 3 = 3 \][/tex]

Next, we combine the results of these multiplications:

[tex]\[ (3x + 1)(3x + 3) = 9x^2 + 9x + 3x + 3 \][/tex]

Now, simplify by combining the like terms (the terms with [tex]\(x\)[/tex]):

[tex]\[ 9x + 3x = 12x \][/tex]

Thus, the trinomial expression is:

[tex]\[ 9x^2 + 12x + 3 \][/tex]

Therefore, the final answer is:

[tex]\(\boxed{9x^2 + 12x + 3}\)[/tex]