Stupid question: equation of a line

AARRRGH

Hello all

I know this is a stupid question but... the equation of a line. Forget about the formula used to calculate it, in simple English, what is the equation of a line measuring.

Is it the "shape" and length of a straight line?

Cheers

SkepticOne

In the equation y=mx+c, m is the slope and c is the value of y as it crosses the y axis.

Mikel

m measures the slope of the line, so it can be flattish or steepish or somewhere in between,
then you take that line and shift it up or down, this is the displacement c

Heggy

It defines the position and angle of the line.
The line defined is infinitely long and the shape is, um straight. Unless you go into curves that's slightly different.

The coefficient of x, when y's coefficient is 1, is the slope. i.e. y=mx+c where m is the slope.
The slope is the rate of change of y to x (dy/dx if you've done that yet).
This means if the slope is 1, the line will be at 45deg (for every 1 that the y increases, x increases 1).
If it's 1/2 for every 1 unit increase of y, there will be 2 for x).
If the slope is 0 it will be a horizontal line.
If you want the angle you can use the calculator to get inverse tan of the slope. i.e shift, tan, [slope].
For a vertical line x increases no amount, which means you would be dividing by zero, giving infinity or undefined (That's why tan 90 doesn't work)

c is the displacement from the origin (0,0)

If you want to get any point on the line, pick a number for x, and then solve for y, your x and y values will be the coordinates for a point on the line.

Do it for a different value of x, or a value of y, and you now have your line and enough information to draw it on a graph. The best way is to find a line by letting x=0 and then y=0, (unless it goes through the origin).

Hope this helps.

*edit
I wrote too much, and then other people got there while I was writing, oh well.

AARRRGH

That's exactly what I was looking for Heggy, thanks!

Heggy

No bother.