Odd function on r, that is, f (0) = 0 = 0 * (0+1)+a.

∴a=0

The second question:

It's really not a function. By definition, functions are one-to-one or many-to-one (x to y).

In this problem, one x can correspond to two y's.

Graphics that you think can be valued.

For example; X=3, y has no solution.

All right, that's it! ! Take it! !