If f(x) = 2x + 1 and g(x) = x − 4, what is (f + g)(−1)?

Correct answer: −6

The governing rule for adding functions is (f+g)(x)=f(x)+g(x). We first evaluate both functions at the required input x=−1. Substitution gives f(−1)=2(−1)+1=−2+1=−1. Similarly, g(−1)=−1−4=−5. Adding the two results yields (f+g)(−1)=−1+(−5)=−6. Therefore option C is correct. An equivalent check is to add the functions first: (f+g)(x)=(2x+1)+(x−4)=3x−3, and then substitute x=−1 to obtain −3−3=−6. Option A can arise from a sign or arithmetic error, option B ignores the negative input, and option D does not follow from either evaluation. Careful substitution preserves the signs.