AP EAMCET202021 Sep 2020Evening ShiftMathematicsBinomial TheoremActual
What is the coefficient of ( y^3 x^8 ) in ((x+y)⁻⁵ ), when ( | y x | < 1 ) ?
Options
- A-35
- B-30
- C-25
- D10
Correct answer
A. -35
Step-by-step solution
Since ((x+y)⁻⁵= 1 (x+y)^5 = 1 x^5 (1+ y x )⁻⁵, | y x | < 1 ) ( ) Coefficient of ( y^3 x^8 in (x+y)⁻⁵ ) ( aligned & = coefficient of y^3 x^8 in 1 x^5 (1+ y x )⁻⁵ & = coefficient of y^3 x^3 in (1+ y x )⁻⁵ & = -5(-5-1)(-5-2) 3 ! =-35 aligned ) Hence, option (a) is correct.