AP EAMCET202017 Sep 2020Evening ShiftMathematicsBinomial TheoremActual
If the (m ) th term is the middle term in expansion of ( (x^2- 1 2 x )²⁰ ). Find coefficient of (T_ m+3 ).
Options
- A( ²⁰ C ₁₃ 2⁻¹³ )
- B(- ²⁰ C ₁₃ 2¹³ )
- C(- ²⁰ C ₁₃ 2⁻¹³ )
- D( ²⁰ C ₁₃ 2¹³ )
Correct answer
A. ( ²⁰ C ₁₃ 2⁻¹³ )
Step-by-step solution
Expansion of ( (x^2- 1 2 x )²⁰ ) contains ' 21 ' terms. So middle term is, ( 20 2 +1=11 ) term ( m=11 ) Now, ( aligned T_ m+3 & =T_ 11+3 =T_ 13+1 & = 20 13 (x^2 )²⁰⁻¹³ (- 1 2 x )¹³ & = 20 13 x^7(-1)¹³ 2¹³, x¹³ aligned ) So coefficient is, ( ²⁰ C ₁₃ 2⁻¹³ ^ )