Question

How do you do 21 and 22?

Answer 1

Answer:

  21.  d.  39

  22.  c.  20; 7

Step-by-step 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

__

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