Đáp án:
D
Giải thích các bước giải:
\(\begin{array}{l}
\mathop {\lim }\limits_{x \to - \infty } \left( {\sqrt {2{x^2} + 2x - 1} + x\sqrt 2 } \right)\\
= \mathop {\lim }\limits_{x \to - \infty } \frac{{2{x^2} + 2x - 1 - 2{x^2}}}{{\sqrt {2{x^2} + 2x - 1} - x\sqrt 2 }}\\
= \mathop {\lim }\limits_{x \to - \infty } \frac{{2x - 1}}{{\sqrt {2{x^2} + 2x - 1} - x\sqrt 2 }}\\
= \mathop {\lim }\limits_{x \to - \infty } \frac{{2 - \frac{1}{x}}}{{ - \sqrt {2 + \frac{2}{x} - \frac{1}{{{x^2}}}} - \sqrt 2 }}\\
= \frac{2}{{ - \sqrt 2 - \sqrt 2 }} = \frac{2}{{ - 2\sqrt 2 }} = - \frac{{\sqrt 2 }}{2}\\
\to a = - 1;b = 2;c = 2\\
\to S = - 1 + 2 + 2 = 3
\end{array}\)
