Find equation of line through point (9, 1) and (4, -3)

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hannah8908

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Aug 23, 2007
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Find the equation of the line that passes through points B and C in the previous problem.
Point B: (9,1)
Point C: (4,-3)

The answer is 4x-5y=31.

I just need to know how to get there. Once I have the first couple of steps I can normally get it by myself, I just don't know how to start.
 
Equation of a line through points (x_1, y_1) and (x_2, y_2) is:
Code: 
   (x - x_1)          (y - y_1)
---------------  =  ---------------
  (x_2 - x_1)        (y_2 - y_1)
 
Upon simplification - did you get the equation you were supposed to find?

If you did - then you must have done it correctly.

Check whether the given points satisfy the equation.
 
hannah8908 said:
so I would have (x-4)/(4-9)=(y-(-3))(-3-1)?
Click to expand...
NO! You're not being CAREFUL: go to your room, no dessert!

(x - 9) / (4 - 9) = (y - 1) / (-3 - 1)
 
Okay, so if I do that then do I cancel the like terms and end up with (x/4)=(y/-3)? or do I actually have to do the operations and then simplify?
 
hannah8908 said:
Okay, so if I do that then do I cancel the like terms and end up with (x/4)=(y/-3)?
Click to expand...
That's entirely WRONG; where do you see "like terms"?
You need to get back to basics...or pay attention in class :shock:
 
hannah8908 said:
Okay, so if I do that then do I cancel the like terms and end up with (x/4)=(y/-3)? or do I actually have to do the operations and then simplify?
Click to expand...

You can only cancel (from numerator and denominator) things that are "factored" out. You cannot cancel out addition or subtraction.

For the above equation - you need to simplify by cross-multiplication (or some other similar method that have been taught to you).
 
I do pay attention in class... I'm a 4.0 student, but I haven't done this stuff in almost 2 years. Thank you Subhotosh Khan that kind of makes sense. I'm just really really bad at math!!! I know, I'm frustrating too because I want to understand every little part so I ask a lot of questions. Thanks for sticking with me both of you.
 
OMG!!! I just got it. It just sort of clicked and now I feel REALLY STUPID!!! Thank you two sooooooooo much.
 
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