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Algebra / Linear functions Difficulty: Medium
The figure presents a 2-column table, with 3 rows of data. The heading for the first column is “x,” and the heading for the second column is “f of x.” The 3 rows of data are as follows. 
Row 1. x, zero; f of x, negative 2. 
Row 2. x, 2; f of x, 4.
Row 3. x, 6; f of x, 16.

Some values of the linear function f are shown in the table above. What is the value of f of 3?

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Explanation

Choice B is correct. A linear function has a constant rate of change, and any two rows of the table shown can be used to calculate this rate. From the first row to the second, the value of x is increased by 2 and the value of f of x is increased by 6 equals, 4 minus negative 2. So the values of f of x increase by 3 for every increase by 1 in the value of x. Since f of 2, equals 4, it follows that f of, open parenthesis, 2 plus 1, close parenthesis, equals, 4 plus 3, which equals 7. Therefore, f of 3, equals 7.

Choice A is incorrect. This is the third x-value in the table, not f of 3. Choices C and D are incorrect and may result from errors when calculating the function’s rate of change.