AP EAMCET2003MathematicsBinomial Theorem
The coefficient of x^5 in the expansion of (1+x^2 )^5(1+x)^4 , is :
Options
- A60
- B50
- C40
- D56
Correct answer
A. 60
Step-by-step solution
We have, (1+x^2 )^5(1+x)^4= [1+ ^5 C₁ x^2+ ^5 C₂ x^4+ + (x^2 )^5 ] [1+ ^4 C₁ x+ ^4 c₂ x^2+ ^4 C₃ x^3+x^4 ] Coefficient of x^5= ^5 C₁ ^4 C₃+ ^5 C₂ ^4 C₁=5 4+10 4=20+40=60