1. Functions of the form f(x)=ax+b, where a is non zero, are called "linear functions" and the graphs of them are inclined lines.
2. If a>0, the line is increasing, so it gets higher as we move x to the right
If a<0, the line is decreasing.
3. There is no x we are not allowed to plug in the function: so Domain = all Real numbers
4. Since the lines are either increasing or decreasing, f(x), represented by the y values, take all values from -∞ to +∞. So Range = all Real numbers.
f(x)=4x (increasing line, 4>0) ,
g(x)=-x+4, h(x)=-4x (decreasing lines, -1<0, -4<0)
all f, g, h have Domain AND Range : All real numbers
