câu 1 sai đề nha. trên tử là căn - căn nha mn. e ghi để sai

CMR

1. \[C_{20}^1 + C_{20}^3 + C_{20}^5 + ... + C_{20}^{17} + C_{20}^{19} = {2^{19}}\]

2. \[{\left( {C_n^0} \right)^2} + {\left( {C_n^1} \right)^2} + ... + {\left( {C_n^n} \right)^2} = C_{2n}^n\]

tính các giới hạn

\[\begin{gathered}
  \mathop {\lim }\limits_{x \to 1} \frac{{\sqrt {5 - {x^2}}  + \sqrt[3]{{{x^2} + 7}}}}{{{x^2} - 1}} \hfill \\
  \mathop {\lim }\limits_{x \to 0} \frac{{2\sqrt {1 + x}  - \sqrt[3]{{8 - x}}}}{x} \hfill \\
  \mathop {\lim }\limits_{x \to 0} \frac{{\sqrt {8{x^3} + {x^2} + 6x + 9}  - \sqrt[3]{{9{x^2} + 27x + 27}}}}{{{x^3}}} \hfill \\
  \mathop {\lim }\limits_{x \to 0} \frac{{{x^3}}}{{\sqrt {\left( {1 + 2x} \right)\left( {1 + {x^2}} \right)}  - \sqrt {\left( {1 + 3x} \right)\left( {1 + 3{x^2}} \right)} }} \hfill \\
\end{gathered} \]

111

Tìm \[\mathop {\lim }\limits_{x \to 1} \frac{{\sqrt[4]{{2x - 1}} + \sqrt[5]{{x - 2}}}}{{x - 1}}\]