Equation of a straight line given two points.

In this tutorial we will look closer at straight lines this time using two given points.

In our last tutorial we learned how to find the Equation of a straight line given one point and slope. If you haven’t read it I invite you to do it and learn some maths.

Every time you want to find the equation of the line you will need two pieces of information to do it, it could be one point and the slope or two points as in these case.

To find the equation of the straight line given two points you will need to follow the next steps:

1. Find the slope. ( m=(Y2-Y1)/(X2-X1))
2. Use point slope equation.(( Y-Y1)=m(X-X1))
3. Solve for Y.
4. Plot the equation.

Example:

Given the points (1,2), (3,4)

when X1=1, Y1=2 and X2=3, Y2=4

1.Find the slope

m=(Y2-Y1)/(X2-X1)

m=(4–2)/(3–1)

m=1

2. Use point slope equation.

( Y-Y1)=m(X-X1)

Change the values in the equations.

(Y-2)=1(X-1)

3.Solve for Y.

(Y-2)=1(X-1)

(Y-2)=X-1

Y=X-1+2

Y=X+1

4. Plot the equation.

To plot the equation we just write it down in our app Quick Graph and you will see instantly the desired plot.

Plot using Quick Graph

If you want to practice your plots or learn more about graphing an equation use Quick Graph.

If you already have Quick Graph, press here to see this equation.