Activity 1. - The y intercept: Understanding theConcept.


Use the StraightLineEqn.xls tool, which displays a graph ofan equation of the form:
y = mx + b.


Do This:

Using the tool, first change the coefficient of xrepresented by m to 2. Then change the constant term represented by b inthe equation, and note the exact differences in the graph. As you do so, try todiscover a relationship between the constant term and the graph. NOTE: Tocomplete a change press the enter key after typing the new value.


Here are some examples. Below each equation note thedifference in the graph.


y = 2x



y = 2x + 4



y = 2x 5



You may try some of your own. When you get the connection,proceed.


Answer these questions:

(a) What relationship do you notice between the y-interceptand the graph? Explain.




(b)              Based on your discovery, explain what you understand they-intercept to be.




(c)               (i) What is the value of b in the equation, y = x ?





(ii) Say what is unique about thegraph of y = x and explain why.










This lesson incorporates the following teaching strategiesbases on the NCTM standards.


In addition the lesson meets the following technologyguidelines specified by Garofolo,Drier, Harper, Timmerman, and Shockey (2000):