Slope of Four-Fifths and Vertical-Intercept of -3

The textbook "Mathematics in Action" had an exercise to graph two points given the following linear equation.

   f(x) = (4/5)x - 3

Zelmo didn't understand the exercise and he was instructed that he needed to pick two inputs and find their respective outputs (i.e. find two ordered pairs to graph). It was suggested he use the input 0 because 0 times anything is 0 (and it gives the vertical-intercept). A second suggested input was 5 because it simplified the arithmetic.

   f(0) = (4/5)0 - 3 = 0 - 3 = -3

   f(5) = (4/5)5 - 3 = 4 - 3 = 1

Zelmo was okay with using 0 for an input value, but he had a difficult time understanding how 5 was picked for the other input value.

Exercises
  1. The slope of function f(x) is _________.

  2. The y-intercept of function f(x) is _______.

  3. The x-intercept of function f(x) is ______.

  4. No or Yes: f(x) is a decreasing function.

  5. f(-5) = _______


Creator: Gerald D. Thurman [gthurman@gmail.com]
Created: 01 February 2007

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