Equation of a Straight Line

(or "y = mx + c" in the UK see below)


Gradient	Y Intercept

y = how far up

x = how far along

m = Gradient or Slope (how steep the line is)

b = the Y Intercept (where the line crosses the Y axis)

Example 1

b = 1

Therefore

y = 2x + 1

-1

–3

b = 0

This gives us y = –3x + 0
We do not need the zero!

Therefore

y = –3x

You can see the effect of different values of m (the slope) and b (the y intercept) at Explore the Straight Line Graph

Country Note

Different Countries teach different "notation":

In the US the notation is:	y = mx + b
In the UK and Malaysia the notation is:	y = mx + c
In Denmark:	y = ax + b
In your country:	let us know!

... but it all means the same thing, just different letters.