If the largest binomial coefficient of (x-2y) n expansion is the fifth term, then the sum of binomial coefficients of all terms of the expansion is___ .

If the largest binomial coefficient of (x-2y) n expansion is the fifth term, then the sum of binomial coefficients of all terms of the expansion is___ .

In the expansion of ∵ (x-2y) n, the binomial coefficient of the fifth term is the largest, ∵ N2 + 1 = 5, ∵ n = 8. The sum of binomial coefficients of all terms in the expansion is 28 = 256