This question belongs to precalculus!
You have to check whether , and you can do this by two ways:
The long way: . Cross multiply this, do a little algebra and reach, finally, , and this must suffice to get the answer.
The short way: factor both the numerator and the denominator of the function: , and you're (almost) done.
Hint: the function isn't 1-1
About onto: you've to check whether has a real solution for some given real number . This is a simple exercise in quadratic and you have to check for which real values of the above quadratic's discriminant is non-negative.
Hint: the function is onto