$^n{C_r}{ + ^n}{C_{r - 1}}$ is equal to
$^{n + 1}{C_r}$
$^n{C_{r + 1}}$
$^{n + 1}{C_{r + 1}}$
$^{n - 1}{C_{r - 1}}$
The solution set of $^{10}{C_{x - 1}} > 2\;.{\;^{10}}{C_x}$ is
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