What is the domain of the function: {(1, 2); (2, 4); (3, 6); (4, 8)}?
A. {1, 2, 3, 4, 6, 8}
B. {1, 2, 3, 4}
C. {6, 8}
D. {2, 4, 6, 8}

Which of the following represents a function?
A.
B.
C.
D.

What is the range of the function: {(2, 1); (4, 2); (6, 3); (8, 4)}?
A. {1, 2, 3, 4, 6, 8}
B. {1, 2, 3, 4}
C. {6, 8}
D. {2, 4, 6, 8

Suppose p varies directly with d, and p = 3 when d = 5. What is the value of d when p = 12? A. 5/4 B. 20 C. 14 D. 36/5

Given the function T(z) = z – 8, find T(–2).
A. –10
B. –6
C. 10
D. 6

The number of calories burned, C, varies directly with the time spent exercising, t. When Dennis walks for 4 hours, he burns 800 calories. Which of the following equations shows this direct linear variation? A. C = t B. C = 800t C. C = 4t D. C = 200t

$$(1)\\the\ domain:\ \ D=\{1;\ 2;\ 3;\ 4\}\ \ \ \ Ans. \ A. \\\\ (2)\ \ ? \ (empty)\\\\(3)\\the\ range:\ \ \ Y=\{{1;\ 2;\ 3;\ 4\}} Ans. \ B.$$

$$(4)\\ \frac{p}{d} =const\\\\ \frac{3}{5} = \frac{12}{d} \ \ \ \Leftrightarrow\ \ \ 3d=5\cdot12\ \ \ \Leftrightarrow\ \ \ d= \frac{5\cdot3\cdot4}{3} =20\ \ \ \Rightarrow\ \ \ Ans. \ B. \\\\(5)\\T(z)=z-8\ \ \ \Rightarrow\ \ \ T(-2)=-2-8=-10\ \ \ \Rightarrow\ \ \ Ans. \ A. \\\\(6)\\800\ calories \ \ \rightarrow\ \ 4\ hours\\x\ \ \ \rightarrow\ \ 1\ hour\\\\x= \frac{800}{4} \ calories\ \ \ \Rightarrow\ \ \ x=200\ calories\\\\C=200\cdot t\ \ \ \Rightarrow\ \ \ Ans. \ C.$$

Note that function means that if x is a number, y will be its function. So according to this definition, y will belong to -
1. d
2. not given
3. b
4. b (as p = 3d/5 as we observe from the data)
5. a ( put z = -2 => T(-2) = z-8 = -2-8 = -10)
6. d (as we observe that for 1 hr calories burned is 200 => for t hrs calories burned is 200 *t =200t)

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