Hi, firstly I've never really understood what injective and surjective means so if someone could give me the gist of that it'd be great! :)

secondly the question i'm stuck on at the moment is....

let A = {x:x (belongs to) [0, (inf))} and B = {x:x(belongs to) [0, inf)} and the function f: A (tends to) B is given by

f(x) = 1/(2+x^2)

show that f(x) is injective but not surjective

Thanks (Happy)