If they are all negative, then x + y + z would be negative, regardless of the values. Since xyz is positive, two of them aren't negative because a negative times a negative is a positive, and we've already ruled out the option of three. Since xy + xz + yz is positive, one isn't negative. Let's say x is the negative one. (It doesn't matter which one we choose because they appear at the same rate) If x is negative, then no matter the values of y and z, it will be negative because you're multiplying them by x. If you factor out the x, you get x( y + z) + yz. So whatever the value of y and z, it will be smaller than x(y + z). This rules out the one option. Sorry I can't explain the third part too well I don't think, It's a little hard to communicate the idea I had.
Hope this helps!
I can't help with the second part, for I am not to good at functions. In the first part, you have three equations saying, if x is between these two numbers, then this is the equation. So it tells us that x = -3, so we know that it's the second equation. So just use a graphing calculator to graph the function f(-3) = (x+2)2 -3