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 Algebra
 Equations of Lines
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Nichelle1012
Junior Member

USA
5 Posts

Posted - 09/26/2013 :  17:21:59  Show Profile  Reply with Quote
Find the equation that has intercepts (0, -7) and (3, 0).

I don't remember how to do this at all. Please explain how to get the answer instead of just giving the answer.



Thanks in advance to everyone who responds. :-)
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Ultraglide
Advanced Member

Canada
299 Posts

Posted - 09/26/2013 :  19:01:10  Show Profile  Reply with Quote
I am sure your text shows you how to find the equation of a line given two points. If you don't have a text, just search the net.
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Nichelle1012
Junior Member

USA
5 Posts

Posted - 09/26/2013 :  21:52:02  Show Profile  Reply with Quote
quote:
Originally posted by Ultraglide

I am sure your text shows you how to find the equation of a line given two points. If you don't have a text, just search the net.





Ultraglide, if I had a textbook to show me, I wouldn't have posted the question for help. I'm not in a class; I am just doing sample problems to em refresh my memory. Also, I have searched the web for help. The website that I am seeking help on is www.mathgoodies.com. As for any other sites, I obviously couldn't find what I'm looking for. Thank you so much. Your reply was SO helpful.
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the_hill1962
Advanced Member

USA
1468 Posts

Posted - 09/27/2013 :  08:51:14  Show Profile  Reply with Quote
Intercepts mean where the graph of the equation crosses the axis.
An x intercept has a point such as (x,0) because any point that is on the x axis would have a y coordinate of zero.
A y intercept has the form (0,y).
If you need more explanation at this point, please ask before reading further.
In your problem, the x intercept is (3,0) and the y intercept is (0,-7)

Hopefully you are familiar with the slope intercept form of a linear equation:
y = mx + b where b is the y intercept and m is the slope.
So, so far you know the equation will have b=-7 since -7 is the y intercept in your problem.
Now to figure out m (the slope).
Hopefully you know how to calculate the slope. If not, look up the formula or ask us. The slope for your points is (-7-0)/(0-3) and that is the fraction 7/3.

So, you can now write the equation
y = (7/3)x - 7
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Nichelle1012
Junior Member

USA
5 Posts

Posted - 09/27/2013 :  11:46:18  Show Profile  Reply with Quote
quote:
Originally posted by the_hill1962

Intercepts mean where the graph of the equation crosses the axis.
An x intercept has a point such as (x,0) because any point that is on the x axis would have a y coordinate of zero.
A y intercept has the form (0,y).
If you need more explanation at this point, please ask before reading further.
In your problem, the x intercept is (3,0) and the y intercept is (0,-7)

Hopefully you are familiar with the slope intercept form of a linear equation:
y = mx + b where b is the y intercept and m is the slope.
So, so far you know the equation will have b=-7 since -7 is the y intercept in your problem.
Now to figure out m (the slope).
Hopefully you know how to calculate the slope. If not, look up the formula or ask us. The slope for your points is (-7-0)/(0-3) and that is the fraction 7/3.

So, you can now write the equation
y = (7/3)x - 7






the_hill1962, thanks!! I do know how to calculate the slope. I got as far as y=(7/3)x-7, but got stuck as to what to do from there. Now I know that you cancel out the (7/3)x and add it to y, which gives (-7/3)x+y=-7. Then I multiply everything by 3, which then gives me the final solution of -7x+3y=-21. Once again, thanks. :-)
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