# Find a if the coefficients of x2 and x3 in the expansion of (3 + ax)9 are equal.

We know that-

General term of expansion (a+b)n is For (3+ax)9

Putting a = 3, b = ax & n = 9

General term of (3+ax)9 is  Since we need to find the coefficients of x2 and x3, therefore

For r = 2 Thus, the coefficient of x2 = For r = 3 Thus, the coefficient of x3 = Given that-

Coefficient of x2 = Coefficient of x3     a = 9/7

Hence, a = 9/7

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos  Greatest term in binomial expansion | Revising Binomial theorem43 mins  Finding remainder using binomial theorem43 mins  Quiz on Greatest term in binomial expansion | Revising Binomial theorem38 mins  Binomial theorem for any index | Interactive Quiz48 mins  Finding coefficient of x^n in binomial expansion59 mins  Lecture on properties of Binomial Coefficients58 mins  Interactive Quiz on properties of Binomial Coefficients51 mins  Master on Binomial Theorem for any index41 mins  Interactive Quiz on Binomial Theorem40 mins  Interactive Quiz | general & middle terms53 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses 