Re: coordinate geometry: linear equations in two variables -- Mathematics Help

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Subject: Re: coordinate geometry: linear equations in two variables

Author:
fizixx

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Date Posted: 18:01:22 12/01/05 Thu
In reply to: Misty Bowman 's message, "coordinate geometry: linear equations in two variables" on 18:06:25 06/18/05 Sat

>what is the equation of the line that contains the
>points with (x,y)coordinates(-3,7) and (5,-1)? I need
>to know how to do this problem step by step.

The equation of a line is:

y = mx + b

m is the slope
x is the independent variable
b is the 'y' intercept
y is the dependent variable

You essentially have to supply 'm' and 'b'.

You can use the following formula:

y - y1 = mx - x1

This is the pont-slope equation, and you have all this information at hand.

m = (y2 - y1)/(x2 - x1)

Let

y1 = -3
y2 = 5
x1 = 7
x2 = -1

It really doesn't matter which ones you pick, as long as the x values correspond to the actual x coordinate given....same for y.. in other words. If you have (8,5)....x = 8 and y = 5. You can't switch this. Understand?

So, plug this in and you will find that m = -8/8 = -1

Then the point-slope equation becomes:

y - 7 = -x - (-3)
==> y - 7 = -x + 3
==> y = -x + 3 + 7
==> y = -x + 10

That's your equation. Hope this makes sense.

fizixx

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Replies:

[> Subject: Re: coordinate geometry: linear equations in two variables
Author: Yvette Jones [ Edit \| View ]	Date Posted: 16:09:10 01/24/11 Mon >what is the equation of the line that contains the >points with (x,y)coordinates(-3,7) and (5,-1)? I need >to know how to do this problem step by step. [ Post a Reply to This Message ]