Answer:
(b) (f+g)(x) = -8x +12; all real numbers
Explanation:
The sum of the functions (f+g)(x) is the sum of the functions f(x)+g(x).
f(x) +g(x) = (6 -6x) +(-2x +6)
= (-6-2)x +(6 +6)
(f +g)(x) = -8x +12
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The domain of any polynomial, or sum of polynomials, is all real numbers.