Cho lim x → x 0 f ( x ) = L < 0 và lim x → x 0 g ( x ) = − ∞ . Kết quả nào dưới đây là đúng?

\(\mathop {\lim }\limits_{x \to {x_0}} f\left( x \right).g\left( x \right) = - \infty \).

\(\mathop {\lim }\limits_{x \to {x_0}} f\left( x \right).g\left( x \right) = + \infty \).

\(\mathop {\lim }\limits_{x \to {x_0}} f\left( x \right).g\left( x \right) = M < 0\).

\(\mathop {\lim }\limits_{x \to {x_0}} f\left( x \right).g\left( x \right) = L\).