Question 390524
Suppose you have this graph:


{{{drawing(400,400,-7,7,-7,7,

graph(400,400,-7,7,-7,7),

line(-8,-3,-4,4), line(3.1,-4.9,8,1), circle(-4,4,.1), circle(-4,4,.05),
circle(-4,4,.15),circle(-4,4,.2),circle(3,-5,.2)
 )}}} 

Now look at its projection upon the x-axis, in green below:


{{{drawing(400,400,-7,7,-7,7,

graph(400,400,-7,7,-7,7),
green(line(-8,0,-4,0), circle(-4,0,.1), circle(-4,0,.05),
circle(-4,0,.15),circle(-4,0,.2),line(3.2,0,8,0),circle(3,0,.3)),


line(-8,-3,-4,4), line(3.1,-4.9,8,1), circle(-4,4,.1), circle(-4,4,.05),
circle(-4,4,.15),circle(-4,4,.2),circle(3,-5,.2)
 )}}} 

Its projection in green upon the x-axis is its domain. So the domain

is the interval notation, taking the x-axis as a number line:

({{{-infinity}}},-4] U (3,{{{infinity}}})

The range is its projection upon the y-axis.  If you extended the
graph far enough the graph will project everywhere on the y-axis, so
the range is ({{{-infinity}}},{{{infinity}}}).  However your graph
may be different.

Edwin</pre>