# Thread: domain of functions 3

1. ## domain of functions 3

how do you find the domain of the function f(x)=9-x over the square root of x+7

2. Originally Posted by bastropgarl
how do you find the domain of the function f(x)=9-x over the square root of x+7
Hi bastropgarl,

$f(x)=\frac{9-x}{\sqrt{x+7}}$

The denominator cannot = 0. f(x ) would be undefined.

x + 7 cannot be negative within the set of real numbers. You would have the square root of a negative number.

So, x + 7 > 0

Therefore, the domain = {x | x > -7}.