To multiply the polynomials \( (2r - 5)(r + 4) \), we can use the distributive property (also known as the FOIL method for binomials).
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Multiply the first terms: \[ 2r \cdot r = 2r^2 \]
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Multiply the outer terms: \[ 2r \cdot 4 = 8r \]
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Multiply the inner terms: \[ -5 \cdot r = -5r \]
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Multiply the last terms: \[ -5 \cdot 4 = -20 \]
Now, we combine all these results together: \[ 2r^2 + 8r - 5r - 20 \]
Combine the like terms \( 8r - 5r \): \[ 2r^2 + 3r - 20 \]
So, the result of multiplying the polynomials is: \[ \boxed{2r^2 + 3r - 20} \]