# Thread: Which expression is defined for all real numbers?

1. ## Which expression is defined for all real numbers?

Which expression is defined for all real numbers?
Please explain why the choice that you chose is correct.

Choice 1)
x+3/x^2

Choice 2)
4/(x-2)^2

Choice 3)
5/(x+2)^2

Choice 4)
7/x^2+3

3. ## Re: Which expression is defined for all real numbers?

big hint: cannot divide by zero

so, what do you think?

4. ## Re: Which expression is defined for all real numbers?

Originally Posted by skeeter
big hint: cannot divide by zero

so, what do you think?
In that case, would it be choice 1 since x could be 0? I still do not understand the question tho.

5. ## Re: Which expression is defined for all real numbers?

Originally Posted by rjg247
In that case, would it be choice 1 since x could be 0. I still do not understand the question tho.
I said, ... cannot divide by zero. Division by zero is undefined.

6. ## Re: Which expression is defined for all real numbers?

They are asking which of the choices is not defined for all real numbers. skeeter told you that you can't divide by 0. So in choice 1 can we let x = 0?

Choice 1 reads $x + \frac{3}{x^2}$ and I'm betting it's supposed to be $\frac{x+3}{x^2}$. These are very different expressions. What you need to write in this case is (x + 3)/x^2.
Similarly choice 4 reads $\frac{7}{x^2} + 3$. Again I'm guessing it's supposed to be $\frac{7}{x^2 + 3}$. What you need to write in this case is 7/(x^2 + 3).