Question:medium
If the coefficients of \( x^3 \) and \( x^4 \) in the expansion of \( (3+kx)^9 \) are equal, then the value of \( k \) is:
If the coefficients of \( x^3 \) and \( x^4 \) in the expansion of \( (3+kx)^9 \) are equal, then the value of \( k \) is:
Show Hint
In the expansion of \( (a+bx)^n \), if the coefficients of \( x^r \) and \( x^{r+1} \) are equal, then \( k = \frac{a(r+1)}{b(n-r)} \). Using this shorthand saves massive amounts of calculation.
Updated On: May 2, 2026
- \( 3 \)
- \( \frac{1}{3} \)
- \( 2 \)
- \( \frac{1}{2} \)
- \( 1 \)
Show Solution
The Correct Option is C
Solution and Explanation
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