Answer:
f(x) = [tex]\sqrt{x+5}[/tex] : All real numbers greater than/equal to 5
Explanation: you can't square root negative numbers, and any number less than 5 would give us negative.
f(x) = [tex]\frac{7}{x-8}[/tex] : All real numbers except 8
Explanation: You can't divide by 0, and if we included 8 in the number set, we would get this: [tex]\frac{7}{8-8} =\frac{7}{0}[/tex] (this is impossible).
f(x) = [tex]\sqrt{2}[/tex] : All positive real numbers and 0
Explanation: Again, you can't square root negative numbers.
f(x) = 8x : All real numbers
Not much to explain for this one, any real number makes this equation true.
