Question

Trying to find the domain of a rational function.
f(x)=3x-8
_________
4x+20

Answer 1

hmm

Answer 2

The domain of the numerator is a polynomial, so the domain is all real numbers.
When it's divided by another polynomial, then the zeroes of the denominator have to be subtracted from the "all real" domain of the numerator.
In this case, the zero of the denominator is x=-5, so the domain of the rational function is
R \ {5} = all real except {5}, sometimes written in interval notation as:
(-inf,5)U(5,+inf).

Answer 3

Thank you not totally understanding it but I will keep practicing

Answer 4

The reason we exclude zeroes from the denominator is because they will make the function undefined.
Since 5 will make the denominator zero, and hence the function undefined, we exclude it from R.

Answer 5

Practice makes perfect! Great!