Math Is Fun Forum

Stanley

Member

Registered: 2006-10-27

Posts: 9

Need to remember the formulae?

For a given linear equation and some (x,y) points, need to know if that lies in the line or above or below the line?

Thanks!

Stanley_Marsh

Member

Registered: 2006-12-13

Posts: 345

Re: Need to remember the formulae?

let give a percific example ,  (3.4) is above or below y=5x+6 ?  if you assume x=3 then y=5x3+6=21 ,21>4, that means the line is above the point.

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Numbers are the essence of the Universe

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Need to remember the formulae?

To elaborate on what Stanley_Marsh has said, to find whether a general point is above, on, or below a general line, you first look at the x co-ordinate of your point.

You then use the equation of the line to work out the corresponding y co-ordinate. If the corresponding co-ordinate is lower than yours, then your point is above the line.
Similarly, if it's equal to yours then the point is on the line and if it's higher than yours then the point is below the line.

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Why did the vector cross the road?
It wanted to be normal.