Tính \(\mathop {\lim \to {{( - 1)}^ - }} + 3x + {x + 1}

* Hướng dẫn giải

\(\eqalign{
& \mathop {\lim }\limits_{x \to {{( - 1)}^ - }} {{{x^2} + 3x + 2} \over {\left| {x + 1} \right|}} \cr
& = \mathop {\lim }\limits_{x \to {{( - 1)}^ - }} {{{x^2} + 3x + 2} \over { - \left( {x + 1} \right)}} \cr
& = \mathop {\lim }\limits_{x \to {{( - 1)}^ - }} {{(x + 1)(x + 2)} \over { - \left( {x + 1} \right)}} \cr
& = \mathop {\lim }\limits_{x \to {{( - 1)}^ - }} \left( { - \left( {x + 2} \right)} \right) = - 1 \cr} \)