Let \( f:\mathbb{R}\rightarrow \mathbb{R} \) be a function such that \( f(x)=\dfrac{x^{2}+2x+1}{x^{2}+1} \). Then:
\( f(x) \) is one-one in \( [1,\infty) \) but not in \( (-\infty,\infty) \)
\( f(x) \) is one-one in \( (-\infty,\infty) \)
\( f(x) \) is many-one in \( (-\infty,-1) \)
\( f(x) \) is many-one in \( (1,\infty) \)