Question

if f(x)={(3,5),(2,4),(1,7)} and g(x)=radical(x-3) what do i do to determine (f+g)(1)

Answer 1

(f+g)(1) is the same as f(1)+g(1).

f(1) is given from the set for f(x). The ordered pair (1,7) means f(1)=7.
g(1) requires calculation from g(x).
\[g(1)=\sqrt{1-3}=\sqrt{-2}=i \sqrt2\]
That answer isn't a real number, so there's two possible answers.
If you're only concerned with real numbers, (f+g)(1) is undefined.
If you're looking at complex numbers, \[(f+g)(1)=f(1)+g(1)=7+i \sqrt2\]