如右图所示,有一定初速度的物体受到一个沿斜面向上的恒定拉力F作用,沿倾角为30°的粗糙斜面向上做直线运动,加速度大小为6m/s2,在物体向上运动的过程中,下列说法正确的是( )
著名学者钱穆认为,唐代“在三省体制下,决策不再是单纯的皇帝个人行为,皇帝的最后决定权包含在政务运行的程式中。”钱穆先生的观点是
Mike lives in Guangzhou. His friend Tom lives in Xi'an. This winter, Tom came to Guangzhou to see Mike. They were very happy to see each other. They asked a lot about each other's family and work. They talked about the weather in their cities, too. Guangzhou is quite warm in winter. It doesn't snow in winter in Guangzhou. Some people in Guangzhou have never seen snow. In Xi'an, it often snows in winter. Children like to play snowball fight and make snowmen. That is great fun. Mike hoped to visit Xi'an next winter.
阅读图文资料,回答下列问题。
材料1:“红色荒漠”是指在我国南方湿润红土地区的土地荒漠化。这些地区地形以丘陵及山区为主,由于高强度的经济活动和滥用资源(主要是砍伐森林),植被覆盖率在30%以下,加之年降水量大且多暴雨,易形成水土流失,土地生产力下降,土地资源丧失,导致红壤裸露,形成“红色荒漠”。
材料2:“红色荒漠”形成结构示意图。
完成反证法证题的全过程.设a1,a2,…,a7是1,2,…,7的一个排列,求证:乘积p=(a1-1)(a2-2)…(a7-7)为偶数.证明:假设p为奇数,则a1-1,a2-2,…,a7-7均为奇数.因奇数个奇数之和为奇数,故有奇数=____=0.但0≠奇数,这一矛盾说明p为偶数.