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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