help me

[loverlychick101]

you lost me when i read about finding the slope. my algebra teacher told us that to find the x's and y's it doesn't matter which one that you name x1 or x2. he said that we could just put either number together. does it matter which number you put as x1 or x2? :?

 

[mattgad]

Hey,

Say you have the points (1, 3) and (5, 9)

You could call (1, 3) x1, and y1. And call (5, 9) x2 and y2

Using the gradient formula:

\(\displaystyle \L \frac{y_2 - y_1}{x_2 - x_1}\\)

You would have:

\(\displaystyle \L \frac{9 - 3}{5 - 1}\ = \frac{6}{4} = \frac{3}{2}\)

However, if you labelled them the other way around.

\(\displaystyle \L \frac{3 - 9}{1 - 5}\ = \frac{-6}{-4} = \frac{3}{2}\)

Same answer means it does not matter which way round they are labelled.

I hope I've helped

 

[stapel]

you lost me when i read about finding the slope....

When who said what about slope, in which thread? I can't even find any other posts under this username...?

To continue a conversation, please post replies and follow-ups to the originating thread, using the original username, so people can know what you're talking about. Thank you.

Eliz.

 

[mattgad]

I presumed that she meant a page on the actual website (not the forum), which confused her.

 

[pka]

I actually agree with your teacher.
I have told students to forget the formula!
Remember slope is change in y divided by change in x.

If A6,7) and B−2,1) going from A to B: x changes by −8 and y changes −6.
But going from B to A: x changes by 8 and y changes 6.
Note that the ratio is the same! The slope is 6/8.

If P1,2) and Q−2,1) going from P to Q: x changes by −3 and y changes −1, so the slope is 1/3 .