When you use the quotient rule to find the derivative of a function, does the denominator of the function have to have a variable or can it be a constant number?
Actually it is indifferent; at the end of the day you get the right answer even if you have a constant in the denominator and you use the Quotient Rule.
The denominator may or may not contain the variable you are deriving for.
Consider that the Quotient Rule deals specifically with this case, i.e., the derivation of a function such as:
In reality you could use the Quotient Rule even if in the denominator you have a constant (it takes only a bit more...steps):
use the Quotient Rule:
Otherwise you could see it as