7.Binomial Theorem
medium

$(1+x)^{20}$ વિસ્તરણમાં મધ્યમ પદ અને $(1+x)^{19}$ ના વિસ્તરણમાં બે મધ્યમ પદોનો સરવાળાનો ગુણોતર મેળવો.

A

$5$

B

$4$

C

$1$

D

$11$

(JEE MAIN-2021)

Solution

Coeff. of middle term in $(1+x)^{20}={ }^{20} C_{10}$

 Sum of Coeff. of two middle terms in

$(1+x)^{19}={ }^{19} C_{9}+{ }^{19} C_{10}$

So required ratio $=\frac{{ }^{20} \mathrm{C}_{10}}{{ }^{19} \mathrm{C}_{9}+{ }^{19} \mathrm{C}_{10}} \frac{{ }^{20} \mathrm{C}_{10}}{{ }^{19} \mathrm{C}_{9}+{ }^{19} \mathrm{C}_{10}}=\frac{{ }^{20} \mathrm{C}_{10}}{{ }^{20} \mathrm{C}_{10}}=1$

Standard 11
Mathematics

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