[Toán 11]chưng minh

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lovelycat_handoi95

[TEX]2C^k_n+5C^{k+1}_n+4C^{k+2}_n+C^{k+3}_n=C^{k+2}_{n+2}+C^{k+3}_{n+3}[/TEX]

\Leftrightarrow[TEX]2C^k_n+2C^{k+1}_n+3C^{k+1}_n+3C^{k+2}_n+C^{k+2}_n+C^{k+3}_n=C^{k+2}_{n+2}+C^{k+3}_{n+3}[/TEX]

\Leftrightarrow[TEX]2C^{k+1}_{n+1}+3C^{k+2}_{n+1}+C^{k+3}_{n+1}=C^{k+2}_{n+2}+C^{k+3}_{n+3}[/TEX]


\Leftrightarrow[TEX]2C^{k+2}_{n+2}+C^{k+3}_{n+2}=C^{k+2}_{n+2}+C^{k+3}_{n+3}[/TEX]


\Leftrightarrow[TEX]C^{k+2}_{n+2}+C^{k+3}_{n+3}=C^{k+2}_{n+2}+C^{k+3}_{n+3}[/TEX]

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