Answer:
The restriction is:
______________________________________________
"
x
" .
______________________________________________Given:
______________________________________________"

" ; The "denominator" cannot be "0"; because we cannot divide by "0" .
___________________________________________________So the restriction(s) on the variable, "x", is that "x" cannot be equal to the value at which the "denominator would equal zero" .
So, set the "denominator" equal to "0" ; and solve for "x" .
9x – 1 = 0 .
Add "1" to each side of the equation:
9x – 1 + 1 = 0 + 1 ;
9x = 1 ;
Divide each side of the equation by "9" ;
9x / 9 = 1/9 ;
x =

.
________________________________So, the restriction is:
________________________________"
x
" .
________________________________