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排列是高考重点考查内容,在历年高考中都出现考题,形式主要是选择题和填空题,主要考查排列的实际应用。考点一:特殊元素、特殊位置的“优先安排法”例1.3名男生,4名女生按下列要求站一排,有多少种站法?(1)甲只能在中间或两端;(2)甲不在最左端,乙不在最右端。【思路点拨】对于“人站队”问题,由于安排甲、乙时有限制,这是有限制条件的排列问题,应优先考虑特殊元素(甲、乙)或特殊位置(左右端),再考虑其他。解:①(特殊元素优先法)先考虑甲有A13种站法,然后其余的
Arrangement is the key examinations of college entrance examination, examination questions in the college entrance examination over the years, the main form of multiple choice and fill in the blank, the main test arrangement practical application. Test site 1: special elements, special location “priority arrangement ” Example 1.3 boys and 4 girls in accordance with the following requirements in a row, how many kinds of station law? (1) A can only in the middle or both ends; ( 2) A is not at the far left, B is not at the far right. [Calling ideas] For the “people stand team ” issue, due to arrangements A, B when there are restrictions, there are restrictions on the arrangement of the problem, priority should be given to special elements (A, B) or special location Consider other. Solution: ① (special element priority method) first consider a A13 kinds of station method, and then the rest