To write the equation that represents the line you have to identify two values:
1) The y-intercept: this is the value of y when x=0
If you watch the graph, the line cuts the y-axis on y=3, this value is the y-intercept of the function.
2) The slope of the function.
Unlike the y-intercept, you cannot determine the slope just by looking at the graphic, you need to do a simple calculation.
Using two points over the line you can apply the following formula to calculate the slope:
For the first set of coordinates I'll use the vlaues (2,6) and for the second set I'll use the y-intercept (0,3), then the slope is
The slope of this line is m=2/3 or if you prefer to write it as a decimal value m=1.5
Now that the slope and the y-intercept are determined you can write the equation folowing the model: y= b+mx
