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# Finding the function

03-10-2015 09:11 PM

How can I find the equation of a segment given by 2 points? Example: a(8,5) and b(5,8)

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## Finding the function

03-11-2015 03:40 PM

@Jucimar_C wrote:

Hi,

How can I find the equation of a segment given by 2 points? Example: a(8,5) and b(5,8)

Many methods. Here's one that works great in CAS (not Home):

line((8,5),(5,8)) ---> y = -x+13

Be sure to type "line" in lowercase letters, or it won't work.

Here's a method that works in both Home and CAS:

simplify(lagrange([[5,8],[8,5]] ) ) ---> -x+13 (the "y=" is implied)

I hope one of these fits your needs. Disclaimer: I don't work for HP. I'm just another Prime user.

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## Finding the function

03-12-2015 07:30 AM

Hi!, Josimar_C:

If you needed know, the conceptual theory, of find, one equation, see ...

a(x1, y1), b(x2, y2) ---> a(8,5), b(5,8)

y= mx + b

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

m=(8 - 5)/(5 - 8)= -3/3 = -1

m= -1( x1- y1) ---> m= -1 (8,5)

y - y1= m( x - x1)

y - 5= - (x - 😎

y - 5= - x + 8

Then, add 5 in (y-5) and 5 in (-x+8)

y-5+5=- x + 8 + 5

y= - x +13

Have a nice day !.

@Maké (Technical Advisor Premium - HP Program Top Contributor).

Provost in HP Spanish Public Forum ... https://h30467.www3.hp.com/

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## Finding the function

03-16-2015 02:19 PM

It took me 8 years to realize that was a french word... 🙂

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.

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## Finding the function

11-15-2017 12:12 PM

Hello Jucimar

Let me suggest you a procedure to be performed in Geometry App. Please take a look at the attached sequence of screenshots. They are in Portuguese, but I guess it won't be a hard time for you

1st) Type both points in Symb view (GA and GB). Then create a line (GC) passing by GA and GB. You can go to Plot view and see how it looks like.

2nd) Go to Num view, choose and empty entry, click on Edit soft button ("Editar") and then in Vars. Select GC and you'll see the line's equation. Check the box if you want to see the equation further in Plot view.

Now, you can move the points and you'll see the chance in the line and its equation.

Regards,

Ciro

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