BITSAT2014MathematicsBinomial TheoremActual
The coefficient of x ⁴ in the expansion of (1+x+x²+x³ )¹¹, is
Options
- A440
- B770
- C990
- D1001
Correct answer
C. 990
Step-by-step solution
We have coefficient of x⁴ in (1+x+x²+x³ )¹¹ array l = coefficient of x ⁴ in (1+ x ² )¹¹(1+ x )¹¹ = coefficient of x ⁴ in (1+ x )¹¹+ coefficient of x ² in 11. (1+ x )¹¹+ constant term is ¹¹ C ₂ (1+ x )¹¹ = ¹¹ C ₄+11 . ¹¹ C ₂+ ¹¹ C ₂=990 array