Question

x+9/x-9 what is the domain?

Answer 1

Remember you cannot divide by zero

So if x-9 is the denominator, then what value of x makes x-9 equal to 0?

Answer 2

9?

Answer 3

(-infinity,9) U (9, infinity)

Answer 4

very good, x = 9 makes x-9 equal to 0

So we must kick 9 out of the domain. Every other real number works in the domain.

Answer 5

So the domain is (-infinity,9) U (9, infinity)