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7.Binomial Theorem
hard
$\left(x^4-\frac{1}{x^3}\right)^{15}$ ના વિસ્તરણમાં $x^{18}$ નો સહગુણક $........$ છે.
A
$5004$
B
$5003$
C
$5002$
D
$5005$
(JEE MAIN-2023)
Solution
$\left(x^4-\frac{1}{x^3}\right)^{15}$
$T_{r+1}={ }^{15} C_r\left(x^4\right)^{15-r}\left(\frac{-1}{x^3}\right)^r$
$60-7 r=18$
$r=6$
Hence coeff. of $x^{18}={ }^{15} C _6=5005$
Standard 11
Mathematics