AP EAMCET2010MathematicsBinomial Theorem
For |x| < 1 5 , the coefficient of x^3 in the expansion of 1 (1-5 x)(1-4 x) is
Options
- A369
- B370
- C371
- D372
Correct answer
A. 369
Step-by-step solution
|x| < 1 5 and 1 (1-5 x)(1-4 x) =(1-5 x)⁻¹ (1-4 x)⁻¹ then by binomial expansion = 1+5 x+25 x^2+125 x^3+ 1+4 x+16 x^2+64 x^3+ the coefficient of x^3 in this expansion is =(125+100+80+64)=369