Let f(x) = x - 1/x. which of the following are zeros of f(x)?
check all that apply: a. x=0 b. x=-1 c. x=1 d. none of the above.

I'm assuming that is f(x) = (x-1)/x
In that case, the answer would be just x = 1.

However, if the original is f(x) = x - (1/x) the answer would be x = 1 and x = -1.

It's really just a formatting thing—if the given equation is indeed f(x) = (x-1)/x then x = 1 is the answer. 

Hope this helped!! xx