5.1, 5.2

In a straight line graph, we use the equation y=mx+c, where ‘m’ is the gradient (Δy/Δx) and ‘c’ is the y-intercept

Now, you will also see this written as ax+by+c=0, where a, b, and c are all integers

You can define a straight line by giving either:

• one point on the line and the gradient
• two different points on the line

The equation of a line with gradient ‘m’ that passes through the point with coordinates (x1,y1) can be written as:

y-y1= m(x-x1)

If we know two different points on the line, we can use the equation:

y-y1/ x-x1 =y2-y1/x2-x1

To recap: