To multiply the polynomial expression \((x + 2)(x - 4)\), we can use the distributive property (also known as the FOIL method for binomials):
\[ (x + 2)(x - 4) = x(x - 4) + 2(x - 4) \]
Now, let's distribute each term:
- \(x(x - 4) = x^2 - 4x\)
- \(2(x - 4) = 2x - 8\)
Now we add those results together:
\[ x^2 - 4x + 2x - 8 \]
Combining like terms:
\[ x^2 - 2x - 8 \]
So, the final result of multiplying \((x + 2)(x - 4)\) is:
\[ \boxed{x^2 - 2x - 8} \]