Provide an example of a continuous function f:R-->R which satisfies all of the following properties

(a) non-decreasing

(b) not constant

(c) not increasing

Be sure to justify your example

I have an example as f( x ) = { 1, x<0 or x, x >= 0 with the graph that the function is constant on the left of the x axis, and increasing on the right of the x axis, but I dont know how to prove this