Ex.( a basic example)
f(x)=x^2 or y=x^2;

this equation is in quadratic form obviously its function is parabolic,
plugging in any real number for x and you will find the value of y, and place this in a table for you to plot or sketch in the graph, after sketching the points u can easily identify those numbers belong to domain and range, as well as by seeing  the table.
          x^2       y;

x=0                0
x=1                1
x=2                4
x=3                9
x=-1               1
x=-2               4
x=-5               25;

if you have observed the above figures, the range(y) can be identified ,all real numbers except less than o and the domain (x) are all real numbers.
Now, if you plot this in a graph, the sketch is a parabola (facing upward) excluding negative in the y axis..