If the constant term in the binomial expansion of (√x - k/x²)¹? is 405, then |k| equals:
If the constant term in the binomial expansion of (√x - k/x²)¹? is 405, then |k| equals:
Option 1 -
9
Option 2 -
1
Option 3 -
3
Option 4 -
2
Asked by Shiksha User
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1 Answer
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Correct Option - 3
Detailed Solution:The general term is T? = ¹? C? (K/x²)? (√x)¹?
= ¹? C? K? x? ²? x? /² = ¹? C? K? x? /²
For the constant term, the power of x is 0.
5 - 5r/2 = 0 ⇒ r = 2
The term is T? = ¹? C? · K² = 405
45 · K² = 405
⇒ K² = 9 ⇒ |K| = 3
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