Answer:
21. d. 39
22. c. 20; 7
Explanation:
21. This is straightforward evaluation of the function. Put the numbers 8 and -5 where x is in the function definition and do the arithmetic. Then find the difference of the results.
f(8) = 3·8 -2 = 22
f(-5) = 3·(-5) -2 = -17
f(8) - f(-5) = 22 - (-17) = 22 +17 = 39
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22. The first part is similar to 21—evaluate the function for x=2.
f(2) = 24 -2·2 = 24 -4
f(2) = 20
Note that this result is sufficient to allow you to choose the correct answer.
However, we can also do the second part. Find x for f(x) = 10
f(x) = 24 -2x
10 = 24 - 2x . . . . . . substitute 10 for f(x)
-14 = -2x . . . . . . . . . subtract 24 from both sides
7 = x . . . . . . . . . . . . . divide both sides by -2