JEE Main2006MathematicsBinomial TheoremActual
If the expansion in powers of x of the function 1 (1-a x)(1-b x) is a₀+a₁ x+a₂ x^2+a₃ x^3+ , then a_n is
Options
- Ab^n-a^n b-a
- Ba^n-b^n b-a
- Ca^ n+1 -b^ n+1 b-a
- Db^ n+1 -a^ n+1 b-a
Correct answer
D. b^ n+1 -a^ n+1 b-a
Step-by-step solution
(1-a x)⁻¹(1-b x)⁻¹= (1+a x+a^2 x^2+ ) (1+b x+b^2 x^2+ . ) coefficient of x^n=b^n+a b^ n-1 +a^2 b^ n-2 + .+a^ n-1 b+a^n= b^ n+1 -a^ n+1 b-a a_n= b^ n+1 -a^ n+1 b-a