Translate it
remember that
translates to 
so we can say it equals y
so
translates to 
we want to find the values of x that make it undefined
well, we know that
must be greater than 0
so we do
it is defined for
x-4>0
add 4
x>4
it is defined for all values such that x>4
remember that
so we can say it equals y
so
we want to find the values of x that make it undefined
well, we know that
so we do
it is defined for
x-4>0
add 4
x>4
it is defined for all values such that x>4