Answer:
3. continuous; 0 ≤ x ≤ 12; 0 ≤ y ≤ 6
4. discrete; domain: {2, 4, 6, 8}; range: {10, 18, 26, 34}
Explanation:
You don't need to "try everything." You only need to learn the vocabulary.
3.
A) A continuous function is one whose graph can be drawn without lifting your pencil. The graph shown is one continuous downward sloping line between the two marked points (0, 6) and (12, 0). The function is continuous.
B) The domain of a function is the horizontal extent of its graph, the set of input values for which output values are defined. This graph extends from x=0 to x=12, so the domain is ...
0 ≤ x ≤ 12
C) The range of a function is the vertical extent of its graph, the set of output values it produces. This graph extends from y=0 to y=6, so the range is ...
0 ≤ y ≤ 6
4.
A) The problem statement tells you the domain is a particular set of positive numbers. If you were to graph it, you would have to lift your pencil between plots of the specific points listed. The function is discrete.
B) The problem statement tells you the domain is a particular set of numbers. It is probably easiest to simply list them:
{2, 4, 6, 8} . . . . . . . . domain; positive even numbers less than 10
C) The expression for y tells you how to find the output values associated with these input values. The list of output values is the range of the function.
y = 4x +2 = 4(2, 4, 6, 8} +2 = (8, 16, 24, 32} +2 = {10, 18, 26, 34}
The range is ...
{10, 18, 26, 34} . . . . . the set of output values from the function
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Additional comment
The graph of the function in problem 4 would be the four specific points (2,10), (4,18), (6,26), (8,34). That's it, the whole graph.