(a + b) ^ n if the binomial coefficients of the tenth and eleventh terms are the largest, what is n? How to calculate the required process

I must have learned binomial expansion. Since two items are the largest, then these two items are equal, which means that n is an odd number
Let n = 2K + 1, then the tenth term is k, the eleventh term is K + 1. K = 9, n = 19
This problem doesn't need calculation~

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