Thread: coordinate

In a coordinate system, if three points (5, 3), (x, 4) and (3, 2) lie on a same line, then find a value of x?


Now, the slope appears to be 1/2 from the two given points.

Does this mean that x will be a number than when used to calculate the slope of the line with any of the other two points will still be 1/2? In this case, 7? Or, do we have to develop the equation of the line and substitute (x,4) into the equation of the line in which case I get 5.

They should both give you the same answer. Can you show a bit more work?

You should get the same answer from both methods, because they are somewhat related. The formula I use for finding the gradient is:



Then, I would use:



To get the equation of the line. But, since both equals to m, I can directly say that:



So, it's the same as making both gradients equal.

A shorter way that I came to.

Rearrange your coordinates so that the y coordinates are in ascending order.

(3, 2) , (5, 3) , (x , 4)

Looking at the y coordinates, it increases by 1 each time. And since all the points lie on a straight line, you can conclude that (5, 3) is the midpoint of (3, 2) and (x, 4). In which case, you will have an arithmetic sequence for the x coordinate too. It's 3, 5 then x. Since it increases by 2, you add 2 to 5 to give 7, the value of x.

In any case, you should get x = 7.

Wow nevermind. Simple arithmetic kills :-p

Hello, sfspitfire23!

Did you make a sketch?

I did . . . and baby-talked my way to the answer.

In a coordinate system, points are collinear.

Find a value of

Code:

      |                                       B
      |                                  (x,4)*
      |                                   *   :
      |                               *       :1
      |                       A   *           :
      |                  (5,3)o - - - - - - - + 
      |                   *   :       ?
      |               *       :1
      |       c   *           :
      |  (3,2)o - - - - - - - +
      |               2
      |
  - - + - - - + - - - - - - - + - - - - - - - +
      |       3               5

Going from to , we move 2 units right and 1 unit up.

Going from to , we move ? units right and 1 unit up.

It is obvious (I hope) that: .

Therefore: .