a.
For This function. The denominator cannot be zero.
i.e 13-x ≠ 0 i.e x≠13
Here the numerator is 1.
So Domain only depends on Denominator.
Domain cannot be 13.
So Domain is R-{13}
b.
For this function The Value inside the root cannot be Negative.
9+x≥0
i.e x≥(-9)
So domain is [9,infinity)
Hope it helps...
Regards;
Leukonov/Olegion.
