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7.Binomial Theorem
hard
$(1+x)\left(1+x^2\right)\left(1+x^3\right) \ldots\left(1+x^{100}\right)$ के विस्तार में $x^9$ के गुणांक का मान है
A
$6$
B
$7$
C
$8$
D
$9$
(IIT-2015)
Solution
$x^9$ can be formed in $8$ ways
i.e. $x ^9, x ^{1+8}, x ^{2+7}, x ^{3+6}, x ^{4+5}, x ^{1+2+6}, x ^{1+3+5}, x ^{2+3+4}$ and coefficient in each case is $1$ $\Rightarrow$ Coefficient of $x^9=1+1+1+\ldots \ldots \ldots+1=8$
Standard 11
Mathematics