One of the most useful forms of the equation of a flat surface isWe have to be able to write the equations of lines in this form. We may have to do this in various ways.

- We are given two points:

Find the line which passes throughand

The gradient of the line is

- We are told a point on the line and the gradient of the line.

Find the equation of the line with gradient 5 which passes through (6,7).

- We are told two perpendicular lines meet at a given point or a given value ofGiven the equation of one of the lines, find the equation of the other line.

A line meets the lineat right angles at the point P whose– coordinate is 2. Find the equation of the first line.

The y – coordinate ofis

The gradient of the line is -2 so the gradient of the perpendicular line is

- We are told a line is parallel to some given line and passes through some point.

The line l is parallel toand passes throughFind the equation of

Since the lines are parallel the gradient