The equation of a line describes every point that is on that line.  A point is of the form (x,y).  If a point is on the line X=2 that means that every point on it must start with two eg (2,3).  

Look at each of these lines and try to work out what their equation would be then point to them and the answer will be displayed.

The equation of this line is

In order to find the equation of a line you need a point and the slope.  then plug into the equation

 

Worked Question
The line L has slope 2 and goes thro' the point a(2,3).  What is its equation?

m = 2 and a(2,3)                               y - y1 = m(x - x1)
                                                         y - 3 = 2(x - 2)
                                                         y - 3 = 2x - 4
  
                                                   - 2x + y = -4 + 3
                                                        -2x+y=-1    Multiply everything by -1
                                                       2x - y = 1 




Exercise