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6.Permutation and Combination
easy
यदि $^{15}{C_{r + 3}} = {\,^{15}}{C_{2r - 6}}$ हो, तो $r$ का मान होगा
A
$2$
B
$4$
C
$6$
D
$-9$
Solution
या तो $r + 3 = 2r – 6$ या
$r + 3 + 2r – 6 = 15,\,\,({\,^n}{C_r} = {\,^n}{C_{n – r}})$
$\Rightarrow$ $r = 9$ या $r = 6$.
Standard 11
Mathematics
