Pre calculus
posted by dian .
find the domain of the given function
f(x)=square root 9x

You know that sqrt(u) has domain u>=0. In this case, u = 9x. So, yu must have
9x >= 0
9 >= x
or, as usually written
x <= 9
or
{x:x<=9}
or
x in (oo,9]
depending on desired notation.