Question 1005501
The domain is given by the points touched by the horizontal line, the function of x (x is the horizontal axis). 
If the line begins at -1 and ends at 7 your domain is -1≤x≤7. So, your domain tells you all the points along the line that are included in your domain from beginning to end.
For domain: Your first point and your last point indicate that all the points in between are your domain.
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When we talk about range, think of y, the vertical axis in the graph. First find the lowest point of the line then the highest point. Your range will show the lowest point and the highest point. Let's assume your the lowest point in your line is 0 and the highest point it touches is 8, though you still write it like: 
0≤x≤8.
For range: The lowest point and the highest point of the line indicate that all the points between the high and the low are your range.