Answer:
[tex]-9[/tex]
Step-by-step explanation:
To find x intercept we will set f(x) to 0
[tex]0=x^2-81[/tex]
Add 81 to both sides
[tex]81=x^2[/tex]
Square root both sides
[tex]9=x[/tex]
There will be 2 x intercepts since x is squared so one will be positive 9 and the other negative 9 but we choose -9 since it is the only one that is an answer choice
I hope this helps
