7.Binomial Theorem
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यदि ${(1 + x)^{20}}$ के प्रसार में $r$ वें एवं $(r + 4)$ वें पदों के गुणांक बराबर हैं, तो $r$ का मान होगा

A

$7$

B

$8$

C

$9$

D

$10$

Solution

$^{20}{C_{r – 1}}{ = ^{20}}{C_{r + 3}}$

$ \Rightarrow $ $20 – r + 1 = r + 3$

$\Rightarrow r = 9$.

Standard 11
Mathematics

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