This is my doubt:

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

Thanks a lot. =)

rth term in the expansion of (b + x)n is . The coefficient of

Here b = 3 and x = ax

According to the question coefficients of x2 and x3 are equal, then,


  • 25

Is a 9/7  ?????????

  • -4

Is 'a' 9/7x because that's what I got and I'm not sure that's right? Anyway, thanks for your answer.

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