Find Equation of a Line

Example on how to find equation of line from a graph.

Example 1

What is the equation of the line shown in the graphs below?

graph_1



  1. $y=\dfrac{1}{3} x + 3$

  2. $7$

  3. $8$

  4. $y=x+3$

  5. $y=3x+3$

Solution


  1. We first determine coordinates of the $x$ and $y$ intercepts

    $x$ intercept :$(-3,0)$ , $y$ intercept : $(0,3)$

  2. We next use the two points to calculate the slope $m$

    $m=\dfrac{3-0}{0-(-3)}=\dfrac{3}{3}=1$

  3. Using the slope and the $y$ intercept, the equation of the line in slope intercept form is given by

    $y=x+3$

    Answer D