Hi Folks,

Just wondering how one derives the equation of a line y=mx+b from this general expression f(x,y)=a+bx+cy. I believe this expression represents plane geometry.

Any thoughts

Regards

bugatti

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- Mar 29th 2013, 04:42 AMbugatti79Equation of a line derivation
Hi Folks,

Just wondering how one derives the equation of a line y=mx+b from this general expression f(x,y)=a+bx+cy. I believe this expression represents plane geometry.

Any thoughts

Regards

bugatti - Mar 29th 2013, 05:31 AMRuunRe: Equation of a line derivation
Pick one point on the plane, say and other one . We will try to see the relation between and Now impose that they are in a line:

Let be the angle between the black and the red segments. We have where and . Then

This is

where and - Mar 29th 2013, 06:16 AMbugatti79Re: Equation of a line derivation
- Mar 29th 2013, 07:13 AMHallsofIvyRe: Equation of a line derivation
f(x,y)= z= ax+ by+ c is the equation of a

**plane**in three dimensions. What do you**mean**by "derive the equation of a line"? Which line? There exist an infinite number of lines in that plane. We could, for example, get the equation of the line where it intersects the xy plane by setting z= 0: 0= ax+ by+ c which is the same as -by= ax+ c and then divide both sides by -b: y= (-a/b)x- (c/b) which is of the form "y= mx+b" with m= -a/b and "b"= -c/b.