# A Couple of Points on Straight Line Graphs...

Here we look at a great way to construct/sketch a straight line graph that requires just two points.

## The two-point gradient and y-intercept method

The equation for a straight line is

Where **x** and **y** are variables that relate to the x and y axes of a graph.

The gradient (slope) of the line is given by **m** - this is the number immediately before the x (it's known as the coefficient). If the coefficient is a **negative** value, the gradient will **slope downwards** on a graph.

The **c** term is the y-intercept - the point on the y-axis where the line will cross.

Look at the following equation...

If it can be manipulated so that it has the form **y = mx + c**, it can be graphed.

In this case, the line will have a **gradient of 3** and will **cross the y-axis at y = 4**.

The line can be graphed quickly by plotting just two points.

The easiest point to plot is the y-intercept. This occurs when x = 0 so the coordinates will be (0, 4)

Another point on the graph is needed and it can be found using the value for the gradient, 3.

The gradient is usually found by calculating...