Function f(x)=4-5x is a linear function and is always increasing or decreasing.This function has slope -5, then the angle between x-axis and the graph of f(x) is obtuse. The graph is passing through points (0,4) and (0.8,0). Drawing this graph on coordinate plane you can see that function is always decreasing, then
Answer: decreasing for [tex]x\in (-\infty,\infty)[/tex]
