BITSAT2012MathematicsBinomial TheoremActual
The coefficient of x²⁰ in the expansion of (1+x² )⁴⁰ (x²+2+ 1 x² )⁻⁵ is
Options
- A³⁰ C ₁₀
- B³⁰ C ₂₅
- C1
- DNone of these
Correct answer
B. ³⁰ C ₂₅
Step-by-step solution
Expression = (1+x² )⁴⁰ (x+ 1 x )⁻¹⁰= (1+x² )³⁰ x¹⁰ The coefficient of x²⁰ in x¹⁰ (1+x² )³⁰= the coefficient of x ¹⁰ in (1+ x ² )³⁰= ³⁰ C ₅= ³⁰ C _ 30-5 = ³⁰ C ₂₅