# domain of functions 3

• January 21st 2010, 11:55 AM
bastropgarl
domain of functions 3
how do you find the domain of the function f(x)=9-x over the square root of x+7
• January 21st 2010, 12:26 PM
masters
Quote:

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}.