Thế này k biết có đùng k -_-$L=\mathop {\lim }\limits_{x \to \infty }\frac{x^{10}(1+\frac{1}{x^2})^5x^{30}(3-\frac{1}{x^3})^{10}}{x^{40}(1-\frac{2}{x^{30}}+\frac{1}{x^{40}})}$
$=\mathop {\lim }\limits_{x \to \infty }\frac{(1+\frac{1}{x^2})^5(3-\frac{1}{x^3})^{10}}{1-\frac{2}{x^{30}}+\frac{1}{x^{40}}}=3^{10}$