Answer:
Because the numerator being zero makes f(x)=0, and zero is a value.
Step-by-step explanation:
The domain of any rational function will be determinated by all values that DO NOT satisfy the denominator, meaning, makes it zero.
When solving the given denominator, they find that -4 and 9 are the values that makes the function equal to zero, which is mathematically incorrect.
Hope this clear your doubts.
