Determine whether f is a function from Z to R. If f is not a function, provide an explanation or an example:
A. f (x) = x -1 (b) f (x) = 1/x
C. f (x) = x2 (d) f (x) = √x
E. f(x) = x3 + 7√
F. f (x) = x2 + 1