Question

The table shows the outputs, y, for different inputs, x:

Input (x) 2 5 9 12
Output (y) 20 15 12 8

Part A: Do the data in this table represent a function? Justify your answer.

Part B: Compare the data in the table with the relation f(x) = 5x + 14. Which relation has a greater value when x = 9?

Part C: Using the relation in Part B, what is the value of x if f(x) = 64?

Answer 1

A Yes as the x values are all different

B f(x) = 5x + 14

when x = 2 , f(x) = 5(2) + 14 = 24
x = 5, f(x) = 39,
Each value of f(x) is greater than corresponding ones in the function in A.
when x = 9 f(x) = 59 which is greater than for first function ( =12)

First function is a decreasing while f(x) is increasing

C f(x) = 64 = 5x + 14

5x = 64 - 14 = 50

x = 10