b) $B = \lim (2n - \sqrt{4n^2+n})=\lim \dfrac{4n^2-(4n^2+n)}{2n +\sqrt{4n^2+n}}=\lim \dfrac{-n}{2n +\sqrt{4n^2+n}}$$=\lim \dfrac{-1}{2 +\sqrt{4+1/n}}=-\dfrac{1}{4}$.
b) $B = \lim (2n - \sqrt{4n^2+n})=\lim \dfrac{4n^2-(4n^2+n)}{2n +\sqrt{4n^2+n}}=\lim \dfrac{-n}{2n +\sqrt{4n^2+n}}$$=\lim \dfrac{-1}{2 +\sqrt{4+1/n}}=-\dfrac{1}{2}$.
b) $B = \lim (2n - \sqrt{4n^2+n})=\lim \dfrac{4n^2-(4n^2+n)}{2n +\sqrt{4n^2+n}}=\lim \dfrac{-n}{2n +\sqrt{4n^2+n}}$$=\lim \dfrac{-1}{2 +\sqrt{4+1/n}}=-\dfrac{1}{
4}$.