1) False, because for each X, there is one value of a(x), but for any given value of a(x), there are 4 values of X.
2) False , for reason of 1) , any polynomial of even degree is not one to one function.
3) True 9√(X + 9) , square root is a positive number, only with one value,
4) True , ratio of 2 linear function is one to one, every one X there is only one value of Y.
5 ) True.