二项式定理揭示了项数、系数、指数等方面的联系与规律,学习时应熟练掌握下面性质. 设 ,则①展开式共n+1项,各项a的指数从n起。逐项减1,直到0为止;b的指数从0起,逐项加1,直到n为止;每项a与b的指数和为n;第r+1项(通项)为Tr+1=C_n~ra~(n-r)br; The binomial theorem reveals the relations and rules of terms, coefficients, indices, etc., and should be proficient in the following properties when learning. For example, the expansion formula is a total of n+1 items, and the indices of each item a start from n. Decrement one by one until 0. The index of b starts from 0, adds 1 to each item until n. The exponent of each item a and b is n. The item r+1 (general item) is Tr+1= C_n~ra~(nr)br;