NDA2024MathematicsBinomial TheoremActual
What is the coefficient of x¹⁰ in the expansion of (1-x^2 )²⁰ (2-x^2- 1 x^2 )⁻⁵ ?
Options
- A-1
- B1
- C10
- DCoefficient of x¹⁰ does not exist
Correct answer
A. -1
Step-by-step solution
(1-x^2 )²⁰ [- ( 1 x^2 +x^2-2 ) ]⁻⁵ aligned & =- (1-x^2 )²⁰ (x- 1 x )⁻¹⁰ & =- (1-x^2 )²⁰ (x^2-1 )⁻¹⁰ x¹⁰ & =- (1-x^2 )¹⁰ x¹⁰ & ~T _ r+1 =- ¹⁰ C _r(1)^ 10-r (-x^2 )^ 10-r x¹⁰ & =(-1)^ 11-r ¹⁰ C _r x^ 30-2 r & 30-2 r=10 & r=10 & Coefficient of x¹⁰=(-1)^1 ¹⁰ C ₁₀=-1 1-1 . aligned