To find the product of the polynomials \( (2x + 1)(x - 4) \), we will use the distributive property (also known as the FOIL method for binomials) to multiply each term in the first polynomial by each term in the second polynomial.
- First, multiply the first terms: \( 2x \cdot x = 2x^2 \).
- Outer, multiply the outer terms: \( 2x \cdot (-4) = -8x \).
- Inner, multiply the inner terms: \( 1 \cdot x = 1x \) or just \( x \).
- Last, multiply the last terms: \( 1 \cdot (-4) = -4 \).
Now, combine these results:
\[ 2x^2 - 8x + x - 4 \]
Next, combine the like terms:
\[ 2x^2 - 7x - 4 \]
Thus, the product of the polynomials \( (2x + 1)(x - 4) \) is
\[ \boxed{2x^2 - 7x - 4}. \]