How do find the domain and range from a graph, and writing it as an inequality

To determine the domain is the same as to determine which numbers appear as the first number (the x-value) in an ordered pair that is part of the graph.
To determine the range is the same as to determine which numbers appear as the second number (the y-value) in an ordered pair that is part of the graph.
Here are some examples:
y
≥
x
2
+
3
graph{y >= x^2+3 [-11.6, 13.72, 0.15, 12.81]}
Although it is not 100% certain from just the graph, this graph does get wider and wider. Every
x
does appear in some ordered pair on the graph. The domain is all real numbers.
The
y
values that appear start at
3
and go up. We get all numbers greater than or equal to
3
. Inequality:
y
≥
3
.
If you've learned interval notation, you write:
[
3
,
∞
)
x
2
+
y
2
9
≤
1
# graph{x^2 + y^2/9 <= 1 [-5.35, 7.14, -3.105, 3.14]}
Domain (x-values) Go from
−
1
to
1
(inequality:
−
1
≤
x
≤
1
)(interval:
[
−
1
,
1
]
)
Range:
−
3
to
3
(inequal:
−
3
≤
y
≤
3
(interval:
[
−
3
,
3
]
)
More challenging:
x
2
+
y
2
<
9
graph{x^2+y^2 < 9 [-5.35, 7.14, -3.105, 3.14]}
The dotted line is not included, so we do not include the points at
−
3
or at
3
.
Domain:
−
3
<
x
<
3
(interval
(
−
3
,
3
)
)
R
a
n
≥
:
-3(
∫
e
r
v
a
l
(-3, 3))
Last one:
x
−
y
2
<
6
graph{x- y^2 < 6 [-9.87, 30.68, -9.96, 10.32]}
Domain: all real numbers
Range: all real numbers