Question

What is the domain of `f(x)= (x^2+18x+18 ) / ( x^2+9x+20)`?

Answer 1

`x inRR`

Explanation:

If we look at the numerator and denominator, they are both quadratics, which are defined and continuous for all real numbers.

Defined and continuous `<=>` `x inRR`

We can plug in any value for `x` and get a value for `f(x)`. It doesn't matter that it's a fraction- even if `x` is zero, we get a value, `9/10`.