How to find the sum of coefficients of binomial expansion

How to find the sum of coefficients of binomial expansion

(AX + by) ^ n, this is a general formula. A and B are constant coefficients, so when x = y = 1, that is, (a + b) ^ n is the sum of all coefficients. This is a skill. No matter how complex X and y are, it can be obtained by only making them 1. You can try it