CAS problem with solution

[Teresa]

Hello all, I just bought a Prime and tried some things out. So I tried to get a solution in CAS mode for the equation lim X->infinity of (sqrt(X*X+2X+1)-sqrt(X*X)). I think the solution should be 1 but i get -infinity.    
The plot of the function gives also 1. I tried it in the simulator (rev6975) and the calculator (rev.6975 CASvers. 1.1.2-11) same result.
What do i do wrong?
Thanks for your help Teresa