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7.Binomial Theorem
normal
The coefficient of $x^{37}$ in the expansion of $(1-x)^{30} \, (1 + x + x^2)^{29}$ is :
A
$0$
B
${}^{29}{C_{12}}$
C
$ - {}^{29}{C_{12}}$
D
None
Solution
$(1-x)^{30}\left(1+x+x^{2}\right)^{29}$
$(1-x)\left(1-x^{3}\right)^{29}$
$\left(1-x^{3}\right)^{29}-x\left(1-x^{3}\right)^{29} \longrightarrow$ Coeff of $x^{37}$
$\mathrm{O}-^{29} \mathrm{C}_{12}(-1)^{12} \Rightarrow-^{29} \mathrm{C}_{12}$
Standard 11
Mathematics