Given:
The graph of y= x^2 - 4
To determine the roots of the equation using the graph, we note
first that real roots of the function (or zeros of the function) represented by the graph are found where the graph crosses or contacts the x-axis.
As we can see on the given graph, it crosses at x= -2, x=2. Therefore, the roots of the equation y= x^2 - 4 are:
x=-2
x=2