Maths Statistics - Line of best Equation

[Crimson]

Y=mX+C
m = ‘Gradient’ and C = ‘Y intercept’

The gradient is how steep the line is. This could be read as how many bars go up as to one bar across, or visa versa. However, I want my results to be as reliable as possible and to do this there is necessary equation. This equation gives the exact gradient of the line:

Change in Y/Change in X

To do this, you have to pick out two clear points on the line of best fit and find the change of the X value and the Y value.

As you can see, the change in the Y value is that of;

9000 – 8000 = 1000

And the change in the X value is that of;

48000 – 40000 = 8000

The next stage is to put these values into the equation and finish the sum.

1000/8000 = 1/8 = 0.125


Thus;
m = 0.125


~~~~~~~~~

Okay, so I have this so far for a small piece in my coursework. However, on my graph.. The line of best fit is negative so there should be a minus in my equation so it should be;
Y=-mX+C

But it's not. lol

I think I've done all the sums correctly but I was talking to a friend about it and he's not sure either. Is the sum correct, and I just need to put a minus in there and simply say,
"As the gradient is negative, a minus is needed." Or is my sum incorrect and is that the reason for the minus not being there?

There are also pictures and stuff in the word document but I can copy and paste them, so when it says "As you can see" you can actually see on the word document

Maaaaaaany thanks

[Crimson]

Woops, nevermind. Found where I went wrong

[DieselShaq]

Well, to answer your question anyway, m is any number and thus, it isn't always positive. So the standard line equation of y=mx+c still stands, except that m is a negative number.

[Smarteh.]

How are you supposed to do this. Lol