To factor the expression \( 45x - 18y + 36 \) completely, we can start by looking for the greatest common factor (GCF) of the coefficients.
- The coefficients are 45, -18, and 36.
- The GCF of these numbers is 9.
Next, we will factor out 9 from the expression:
\[ 45x - 18y + 36 = 9(5x - 2y + 4) \]
Now we need to check if the expression inside the parentheses, \( 5x - 2y + 4 \), can be factored further.
Unfortunately, \( 5x - 2y + 4 \) does not factor nicely using integers or simple monomials, as it doesn't have any common factors or can be rewritten as a product of simpler polynomials.
So, the completely factored form of the expression \( 45x - 18y + 36 \) is:
\[ \boxed{9(5x - 2y + 4)} \]