Is the answer a) for the first image??
Looking at the equation, you look at the x and think what CAN'T x be? Well the denometre cannot be LESS than zero, because negative numbers cannot exist under a square root. So, you go x^2 - 4 > 0 and solve for x.
You'll get x = 2 and -2.
Then you can look at the equation and figure out what type of graph it is, 1/x is hyperbola, so we know the shape of this graph. We can graph a quick sketch to get an idea of it's shape. So the domain is going to be x < -2 and x > 2, and you can see that on the graph - that it makes sense.