Answer:
 (a) (f+g)(x) = √(2x) +x²
 (b) (f-g)(x) = √(2x) -x²
 (c) (f·g)(x) = x²√(2x)
 (d) (f/g)(x) = (√(2x))/x²
Explanation:
These are all about the meaning of the notation (f <operator> g)(x). When the operator is an arithmetic operation (addition, subtraction, multiplication, division), the notation means the same thing as ...
 f(x) <operator> g(x)
__
(a) (f+g)(x) = f(x) + g(x)
 (f+g)(x) = √(2x) +x²
__
(b) (f-g)(x) = f(x) -g(x)
 (f-g)(x) = √(2x) -x²
__
(c) (f·g)(x) = f(x)·g(x)
 (f·g)(x) = x²√(2x)
__
(d) (f/g)(x) = f(x)/g(x)
 (f/g)(x) = (√(2x))/x²