Wednesday, October 11, 2006
posted by man at 6:13 PM
Todays math class we talk about the 3 methods in graphing. Im here to explain again this methods so that we can all understand it.
Graphing Method #1 (Table of Values)
- "table of values" shows the relationship between x and y given by any equation.
We can pick any value for x and use the equation to solve y.
y=x+1 (y is equal to the value of x plus one)
let x = 1
y=x+1 Each one of this pairs values represents
y=1+1 a points on our line. These are then easily
y=2 graph.
let x = 2
y=x+1
y=2+1
y=3
let x = 3
y=x+1
y=3+1
y=4
Graphing Method # 2 (Intercept)
- When you speak of intercepts, it helps to know which one you're referring to.
In the plane, unless a line is parallel to either the x-axis or the y-axis, it will intersect
both axis sometime. We know this because two non-parallel lines in the same plane
will intersect sometime.

x-intercept
The x-intercept is where the graph crosses the x axis.

The word 'intercept' looks like the word 'intersect'.
Think of it as where the graph intersects the x-axis.

With that in mind, what value is y always going to be on the x-intercept? No matter
where you are on the x-axis, y’s value is 0, that is a constant.
eg.


y-intercept
If the x-intercept is where the graph crosses the x-axis where do you think the graph crosses for the y-intercept? If you said the y-axis, you are absolutely right.

This time it is x’s value that is 0. Any where you would cross the y-axis, x’s value is always 0.
eg.
Graphing Method #3 (Slope-Intercept)
- The slope of a line measures the steepness of the line.
- Most of you are probably familiar with associating slope with "rise over run".

Rise means how many units you move up or down from point to point.
On the graph that would be a change in the y values.

Run means how far left or right you move from point to point. On the graph,
that would mean a change of x values.
*equation: slope = y=mx+b
eg.
Every straight line can be represented by an equation: y = mx + b.
The coordinates of every point on the line will solve the equation if you substitute
them in the equation for x and y.
The slope m of this line - its steepness, or slant - can be calculated like this:
m = change in y-value
change in x-value
*if theirs question ask me..
next one to blog is jessica
 



3 Comments:


At October 12, 2006 7:24 PM, Blogger Ms. Armstrong

Emman, I'm impressed!!! You had a very hard lesson to scribe for because the class was all discussion based - no notes. You have done a terrific job explaining the 3 methods. The visual presentation could use some work. Maybe you could do a bit of editting. Using a black font on a black background is difficult to read. Some of the formatting is also somewhat crammed. See what you can do to emphasize the excellent content that you have produced.

 

At October 24, 2006 8:01 PM, Blogger Kelley

Thank you to whoever wrote this, I didn't completely understand the whole "intercept" concept and now I do. My question is not how to change the colour of graphs but how do you make them?

 

At November 07, 2006 7:28 AM, Blogger Colin K

Great Post Very Well Explained, And A Great Help!