Question

Find the domain of each o the following rational functions.

f(x)=3x-8
4x+20

Answer 1

3x-8 domain = R (set of all real numbers
4x + 20 = R

Answer 2

domain is the values x is allowed to have in the function. x can take on any value in either of those, so the domain is -infinity to +infinity, or all real numbers.

Answer 3

So you aren't suppose to solve this?

Answer 4

I like trying but i can't get this

Answer 5

wait, is your question (3x-8)/(4x+20)? or 2 different questions?

Answer 6

Yeah it's f(x)=3x-8 divided by 4x+20

Answer 7

OK, so since you're not allowed to divide by zero, x can be anything EXCEPT the value that would make the denominator zero.

Answer 8

so 4x + 20 = 0, solve for x, then the domain is "all x not equal to that number."

Answer 9

Is it x=-5

Answer 10

I'm not understanding

Answer 11

right, so at x=-5 the function blows up. So the domain is anything BUT x = -5. See the graph: http://bit.ly/lBsh9u

Answer 12

yes the number is -5

Answer 13

That's it
F(x)= -5

Answer 14

the answer to "what is the domain" is "all x not equal to -5."

Answer 15

So f(-5)= 3(-5)-8/-20+20 f=-3 huh

Answer 16

I don't understand what you're asking / saying there. yes, f(-5) is undefined because of division by zero.

Answer 17

I'm trying to figure it out and solve it

Answer 18

figure what out? you already have the answer. The domain of a function is all values x is allowed to take in the function. In this case, x can take any value except those which cause division by zero. That's where x = -5. So the answer is "x can be anything except negative 5." You already figured it out!

Answer 19

ohhhh lol oops