Linear equations are written as  y = C1x + C2  where C1 & C2 are  
constants. They are graphed by plugging in numbers for y or x and solve 
for the other. For example if you have an equation y = 3x + 6 you then 
for y = 1 you have 1 = 3x + 6 -> x = -5/3  you then take the two 
coordinates (-5/3,1) and plot the point do this for further numbers and 
connect the points with a straight line. Shifting the graph up or down 
will change the value of C2 and shifting the graph left or right will 
change C1.