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.

 

 

 

 

 

 

 

TEACHER NOTES

 

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):