How do I find the domain of this? f(x) = 3x/x-9 ??

Answer 1

The denominator should not be zero.
If f(x)= 3x/(x - 9) exclude values of x for each x-9=0
from the set of real numbers.

x-9=0 <-> x=9

Thus , the domain is R-{9}
or all the real numbers but 9.

Answer 2

The domain of an equation is all values of x for which the function is defined. In this case, the only time the function is undefined is when the denominator equals 0. The only number which will make your denominator equal to 0 is 9. So the domain of the function is all real number except where x = 9, or in interval notation it is (-infinity, 9) U (9, infinity)

Answer 3

because division by zero is undefined, set the denominator equal to zero and solve for x

x-9 = 0 then x = 9

if 9 is substituted in for x, the problem becomes

f(9) = 3(9) / 9-9 or 27/0 which is undefined.

The domain can be defined as {xI x not = 9}

or (- infinity, 9) U (9, infinity)

Answer 4

Just don't let the denominator be zero. No one likes a fraction with zero on the bottom. ;)

That would happen if x were 9. So the domain is

(-infinity, 9), (9, infinity) [open intervals]

Answer 5

domain is x≠9