If the term independent of x in the expansion of x - k x 2 10 is 405 , then k =

Question

If the term independent of x in the expansion of x - k x 2 10 is 405 , then k =, 3 only, - 3 only, ± 3, 0

MARKS App · Accepted Answer

T r + 1 = 10 c r · x 10 - r 2 - k r · x - 2 r ⇒ 10 - r 2 - 2 r = 0 ⇒ 10 - r = 4 r ⇒ r = 2 T 3 = 10 c 2 ( - k ) 2 = 405 ⇒ 45 k 2 = 405 ⇒ k 2 = 9 ⇒ k = ± 3

Search any question & find its solution

Looking for more such questions to practice?