C
cuccuong


dạng này rất là hay










chứng minh rằng:
[TEX] \frac{C_n^0}{C_{n+2}^1} +\frac{C_n^1}{C_{n+3}^2} +\frac{C_n^2}{C_{n+4}^3} +...+\frac{C_n^k}{C_{n+k+2}^{k+1}} +...+\frac{C_n^n}{C_{n2+2}^{n+1}} = \frac{1}{2} [/TEX]
chứng minh rằng:
[TEX] \frac{C_n^0}{C_{n+2}^1} +\frac{C_n^1}{C_{n+3}^2} +\frac{C_n^2}{C_{n+4}^3} +...+\frac{C_n^k}{C_{n+k+2}^{k+1}} +...+\frac{C_n^n}{C_{n2+2}^{n+1}} = \frac{1}{2} [/TEX]
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