Answer:
the answer is
f(x)=1/√(x-3)
Explanation:
we know that
case a) f(x)=3x
the domain is all real numbers------> interval (-∞,∞)
case b) f(x)=√x
the domain is all real numbers greater or equal than 0
the interval [0,∞)
case c) f(x)=3x+4
the domain is all real numbers------> interval (-∞,∞)
case d) f(x)=1/√(x-3)
the denominator can not be zero and can not be negative
so
(x-3) > 0-----> x > 3-----> the domain is all real numbers greater than 3
the interval is (3,∞)
the answer is
f(x)=1/√(x-3)