$\lim \limits_{x \to \infty} [ \sqrt {x^2+2x-1}-x]$ is equal to :

$\begin {array} {1 1} (a)\;\infty & \quad (b)\;\frac{1}{2} \\ (c)\;4 & \quad (d)\;1 \end {array}$

$(d)1$
answered Nov 7, 2013 by