Which of the following functions is (are) even, odd or neither:

Options

A. 1) `f (x) =sqrt(1+ x+ x ^(2)) -sqrt(1-x+ x ^(2))`
B. 2) `f (x) =x ((a ^(2)+ 1 )/(a ^(x) -1))`
C. 3) `f (x) =log _(10) ((1-x ^(2))/(1 + x ^(2)))`
D. 4) `f (x) =k` (constant)

Answer

A