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i_am_shy


Giải PT:
$P_{n + 5} = 15A_{n+1}^k . P_{n + 4 - k}$
$C_n^6 + 3C_n^7 + 3C_n^8 + C_n^9 = 2C_{n+2}^8$
$A_x^3 + 2C_{x+1}^{x-1} - 3C_{x-1}^{x-3} = 3x^2 + P_2 + 159$
$P_{n + 5} = 15A_{n+1}^k . P_{n + 4 - k}$
$C_n^6 + 3C_n^7 + 3C_n^8 + C_n^9 = 2C_{n+2}^8$
$A_x^3 + 2C_{x+1}^{x-1} - 3C_{x-1}^{x-3} = 3x^2 + P_2 + 159$
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