Question

Let f(x) = 3x + 5 and g(x) = x - 4.
Find f o g and its domain
Answer choices
3x + 1; all real numbers
3x + 1; all real numbers except x = 4
3x - 7 ; all real numbers
3x - 17; all real numbers except x = 4

Answer 1

The answer is 3x - 7 ; all real numbers

f(x) = 3x + 5
g(x) = x - 4

(f o g)(x) = f(g(x)) =
              = f(x - 4) =
              = 3(x - 4) + 5 = 
              = 3x - 12 + 5 =
              = 3x - 7