Let f:(−∞,0]→[1,∞) be defined as f(x)=(1+−x)−(−x−x), then f(x) is
injective but not surjective
injective as well as surjective
neither injective nor surjective
surjective but not injective
f(x)=(1+−x)−(−x−x)
=1−x,x≤0
Then 1−x≥1
Hence function is injective and surjective