MORE MATHS! Finding gradients!

Mollie_Hollie

How do you find a gradient of a line using 2 co-ordinates! :eek:

Reply 1

chr15chr15

change in y divided by change in x

Reply 2

Mollie_Hollie

sorry! i mean equation and the gradient..
im bloody useless at maths!

Reply 3

RoadWarrior

(y2-y1)/(x2-x1)

Change in the 'y' co-ordinates divided my change in 'x' co-ordinates

Reply 4

RoadWarrior

y-y1=m(x-x1)

To find the equation

Reply 5

Smoosh

I'm not sure if I can explain this right, but I have an example that I did a while ago, I hope it's what you mean.

So, y = mx + c

To find the gradient to look at the second point on the line (which is usually labelled B) look at the value for y. In the example I'm using it's -1. Now look at the first point on the line (usually labelled A), in this case the y value is 5. Now take away the second value from the first, so -1 - 5. Then look at x of point B, in this case it's 2 and then the x co-ordinate for point A, which is -1. Now do the second one minus the first, so 2 - - 1. When you have these values you must divide them (y value divided by x value), in this case -1 - 5 = -6 and 2 - - 1 = 3
So it's 6/3 which equals -2

This is the gradient, so the equation is y = -2x + 5
(because c is the y-intercept, so you can see this by looking at the co-ordinates)

I hope this made sense, it looks kind of conufsing.

Reply 6

Mitchy0283

If you just want to find the equation for GCSE use Y=mx+c

For example you know the gradient of the line is say 3, and you have a coordinate (1,1)

Then 1=3(1)+c
Therefore c= -2
So y=3x - 2

For Gradient it is simple your change in y coord OVER change in x

Or dy/dx

For example two points (1,1) and (6,2)

Dy/Dx = 2-1/6-1 = 1/5

Hope that helped :smile: