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AP EAMCET · Maths · Binomial Theorem

If the term independent of x in the expansion of x-kx210 is 405, then k=

  1. A 3 only
  2. B -3 only
  3. C ±3
  4. D 0
Verified Solution

Answer & Solution

Correct Answer

(C) ±3

Step-by-step Solution

Detailed explanation

Tr+1=10cr·x10-r2-kr·x-2r ⇒10-r2-2r=0 ⇒10-r=4r ⇒r=2 T3=10c2(-k)2=405 ⇒45k2=405 ⇒k2=9 ⇒k=±3