Follow-up on my last post

SlowlyFading · 2012-06-27 03:01:45

I understand what the slope is and what the points are for a point-slope problem for example:

y-4= -3(x-2)
The slope of the equation is -3
The point from this equation is (2, 4)

And the same in slope-intercept.

And I understand how to get the slope-point form from two points. But 1,115.00 and 5,83.00 aren't my points, they're coordinates, right? And I don't know how you draw points from coordinates..

bobbym · 2012-06-27 03:04:25

Hi;

One thing at a time. You are jumping ahead to things you do not need to answer this question. Please try this one:

An ordered pair that makes up a point is (x1,y1)

Okay, so which one is x1 in (1,115)

SlowlyFading · 2012-06-27 03:06:31

(x1, y1) then it would be (1, 1).

bobbym · 2012-06-27 03:08:59

Hi;

No, x1 is the first number in the pair (1,115)

SlowlyFading · 2012-06-27 03:11:32

x1 is 1?

bobbym · 2012-06-27 03:12:29

Yes! And what is y1?

SlowlyFading · 2012-06-27 03:13:40

y1 would be the second number in the coordinates so also 1?

bobbym · 2012-06-27 03:15:16

Hi;

The coordinates are (1,115). The first number is the x coordinate, the second number is the y coordinate. Now, what is y1?

SlowlyFading · 2012-06-27 03:17:01

1

bobbym · 2012-06-27 03:17:49

Hi;

What is the second number of (1,115)?

SlowlyFading · 2012-06-27 03:18:26

5?

bobbym · 2012-06-27 03:20:24

(1,115) are two numbers. 1 and 115. The first number is the x coordinate and the second number is the y coordinate. Later we will look at the graph to understand this. Now, please try agin if x1 = 1 what does y1 equal?

SlowlyFading · 2012-06-27 03:21:21

115?

bobbym · 2012-06-27 03:22:46

Correct!
So x1 = 1 and y1 = 115.

Remember the formula?

SlowlyFading · 2012-06-27 03:27:11

Won't I also need to use the other set of coordinates as well? (x2, y2) = (5, 83)

bobbym · 2012-06-27 03:28:16

Hi;

You will be able to answer that for yourself when you plug in what you already have.

SlowlyFading · 2012-06-27 03:50:24

So the point-slope form is y + 115 = -32/-2(x - 1) I believe.

bobbym · 2012-06-27 03:54:59

Hi;

No, that is not correct. Let's look at the formula.

The y1 = 115 so just plug it in to the formula where there is a y1.

You try the x1

SlowlyFading · 2012-06-27 03:59:29

That's the formula I used. I subtracted 83 - 115 and got -32, and subtracted 5 - 1 and got -2.

bobbym · 2012-06-27 04:01:26

Hi;

You are jumping ahead one step at a time will get this done.

Did you see where the y1 went?

SlowlyFading · 2012-06-27 04:08:35

Yes I understand where the y1 went, at least i think I do. You put it in so you could subtract it from the 83 right?

bobbym · 2012-06-27 04:12:22

What 83?

SlowlyFading · 2012-06-27 04:15:26

The y2 83 from the second set of coordinates.

bobbym · 2012-06-27 04:17:07

You only need one set of coordinates we agreed to use (1,115) the (5,83) is not necessary.

SlowlyFading · 2012-06-27 04:20:22

This is the formula my lesson uses:

Example 1: Find the equation of the line through the points (2, -1), (-4, 3)
First, find the slope as we did in lesson 11.
(y2 - y1)
(x2 - x1)
(3 - -1)
(-4 - 2)
(4)
(-6)
So our slope is -2/3

Next, pick one of the points (either one will do) to put into the equation y -k = m(x - h). Be sure to change the signs of the coordinates.

y + 1 = -2/3(x - 2

Math Is Fun Forum

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Re: Follow-up on my last post

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