The sign of y' is not obvious from a first sight.
So let's see what the second derivative is...
It is 0 if x=2. If x<2, y''<0, if x>2, y''>0
It means that y' decreases if x<2 and increases if x>2.
There is a minimum at x=2 for y'.
and is obviously >3.
m is a minimum for y.
From this, you can deduce that y' is always positive, since for any x, we have .
Therefore, y is always increasing.
Now, study the limits of y as x goes to -infinity and +infinity, and see if you can have y=0