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钟绍华 《第二课堂(小学)》2006,(8)
与两直线位置关系有关的试题在高考中一般以选择题的形式出现,难度中等,但有一些陷阱,稍不留意,就会陷入.一、忽视概念例1已知直线l1:x+my+6=0与l2:(m-2)x+3y+2m=0平行,则m的值为()A.3或-1B.-1C.3D.-3或1错解由已知得l1∥l2,m≠0,m-2≠0,且-m1=-m3-2,解得m=3或m=-1.选A.剖析两直线平行指的是两条不重合的直线平行,要跳出陷阱,可在解题后进行验证.当m=-1时,两条直线是重合的,故舍去.应选C.二、忽视斜率不存在例2经过点(1,0)且与直线y=-x+3成45°角的直线方程是()A.y=0B.x=0C.x=1D.y=0或x=1错解设所求方程为y=k(x-1),由1k+k-·(-(1-1))=ta… 相似文献
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教材是进行高考数学复习的主要依据,回归教材是高考复习的必要环节,在第一轮复习即将结束之时,本刊特组织高三的一线教师,对同学们在平时做题中出现的部分知识盲点进行诊断,同时在教材中找到与之相对应的知识,旨在加大同学们对教材的重视程度,便于同学们查漏补缺。 相似文献
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The negative valve overlap (NVO) strategy of HCCI operation was experimentally investigated on a gasoline HCCI engine operated with variable valve timing in association with the addition of diesel fuel. The experimental results show that, by using gasoline and diesel blended fuels, the required NVO interval for suitable HCCI combustion under a given engine speed and a moderate compression ratio condition could be reduced, and the HCCI combustion region was extended remarkably without substantial increase in NOx emissions under a given inlet and exhaust valve timing due to the improvement of charge ignitability. In addition, the possible scale of NVO was extended. A substantial increase in the lean limit of excess air ratio and the upper limit of load range can be achieved because of higher volumetric efficiency, resulting from the decrease in the required NVO and the presence of less residual gases in cylinder. 相似文献
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教材是进行高考数学复习的主要依据,回归教材是高考复习的必要环节.在第一轮复习即将结束之时,本刊特组织高三的一线教师,对同学们在平时做题中出现的部分知识盲点进行诊断,同时在教材中找到与之相对应的知识,旨在加大同学们对教材的重视程度,便于同学们查漏补缺. 相似文献
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钟绍华 《第二课堂(小学)》2006,(6)
递推问题是近几年高考中的热点问题,而迭代法、迭加法和迭乘法是解决递推问题的常用方法,下面结合2005年高考题简单介绍这三种方法． 相似文献