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7.Binomial Theorem
hard
यदि $\left(x+x^{\log _{2} x}\right)^{7}$ के प्रसार में चौथा पद $4480$ है, तो $x ( x \in N )$ का मान है
A
$2$
B
$4$
C
$3$
D
$1$
(JEE MAIN-2021)
Solution
${ }^{7} C _{3} x ^{4} x ^{\left(3 \log _{2}^{x}\right)}=4480$
$\Rightarrow x ^{\left(4+3 \log _{2}^{x}\right)}=2^{7}$
$\Rightarrow \quad(4+3 t ) t =7 ; t =\log _{2} x$
$\Rightarrow t =1, \frac{-7}{3} \Rightarrow x =2$
Standard 11
Mathematics