# Co-ordinate Geometry

## In this topic you learnt:

1. Distance, midpoint, gradient
2. Parallel and perpendicular lines
3. Graphing linear equations
4. The gradient-intercept equation (y=mx+b)
5. General form (ax + by + c = 0)
7. Finding the equation of a line
8. Equations of parallel and perpendicular lines

## 1. Length, midpoint and gradient of an interval

You will need to use the formulae below. I have also hyperlinked videos for each of the formulae

## 2. Parallel and perpendicular lines

Parallel lines have the same gradient

Perpendicular lines have gradients whose product is -1

## 3. Graphing linear equations

• To find the x-intercept, substitute in y=0 and solve the equation
• To find the y-intercept, substitute in x=0 and solve the equation
• A point lines on a line if its (x, y) coordinates satisfy the equation of the line

Horizontal and vertical lines:

Algebra - How to Find Slope, Y-Intercept and Graph a Line

## 4. The gradient-intercept form y=mx + b

The equation of a straight line is y=mx + b where m is the gradient, and b is the y-intercept
Beginning with the y=mx+b format

## 5. General form ax + by + c = 0

A linear equation can be written in the form ax + by + c = 0, where a,b, and c are integers and a is positive.

To find the gradient of this line we write m= - b/a

Changing from slope-intercept form to general form

## 6. Point gradient form

You need to be able to find the equation of a line using the point-gradient formula. You may be given the gradient or you may have to find it.

## 7. Finding the equation of a line

There was no formulae for this section.

## 8. Equations of parallel and perpendicular lines

For parallel and perpendicular lines...