7.Binomial Theorem
normal

 $\sum\limits_{r - 1}^{11} {(x + r)\,(x + r + 1)\,(x + r + 2)...\,(x + r + 9)}$ ના વિસ્તરણમાં $x^9$ નો સહગુણક મેળવો 

A

$5511$

B

$5151$

C

$1515$

D

$1155$

Solution

Required coefficient is

$=(1+2+\ldots+10)+(2+3+\ldots+11)+\ldots$

$…….. + \left( {11 + 12 + … + 20} \right)$

$=5(11+13+\ldots+31)=1155$

Standard 11
Mathematics

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