JEE Main & Advanced
Mathematics
Binomial Theorem and Mathematical Induction
Question Bank
General term, Coefficient of any power of x, Independent term, Middle term and Greatest term and Greatest coefficient
question_answer
The coefficient of \[{{x}^{3}}\] in the expansion of \[{{\left( x-\frac{1}{x} \right)}^{7}}\] is [MP PET 1997; Pb. CET 2001]
A)14
B)21
C)28
D)35
Correct Answer:
B
Solution :
\[7-2r=3\Rightarrow r=2\] \[\therefore \] The coefficient is\[^{7}{{C}_{2}}=21\].