The binomial theorem itself determines the binomial coefficient by permutation and combination. From this point of view, it is not wrong to say that binomial theorem can be solved by permutation and combination. But since it is called theorem, it naturally has its own usage. Therefore, it is more convenient to apply the theorem directly to binomial problems. It should be noted that the solution of binomial coefficient can be extended to trinomial or even polynomial, which is the embodiment of permutation and combination.