Is the function Odd? How can you tell?

Question

You are given the following functions.

(I) y = (x-1)/(x^2+1)
(II) y=(x^2-1)/(x^2+1)
(III) y=(x^2+1)/(x^2-1)

 

(d) Which of the function(s) are odd functions? (Select all that apply.)
(I)
(II)
(III)
none of these

I put one, but I am not entirely sure how to tell when it's odd like I can on other functions. They are L shaped and I am very confused on how to classify if its odd or even on these graphs. Please help me. Thank you!

Answer 1

f(x) is an odd function is f(-x) = -f(x).

For each of the equations substitute -x. If the result is the opposite, the function is odd.