Range corresponds to the values of y on the y-axis. If we see the graph the minimum value of the y-coordinate is -2 and then it tends to increase from it. We do not know till where the y values will increase in the figure it shows 6 but it's still actually increasing we keep on tracing the graph but the minimum value will always remain the same which is -2 . So we can say that the range of the function is
Where f(x) is the function and since the values of y on the y-axis increase from -2 we can say that the function has the range of values greater than or equal to -2