某人在国庆节那天,上午7时,乘摩托艇以匀速v(4≤v≤20)海里/小时从A港出发到距50海里的B港去,然后乘汽车以速度w(30,≤w≤100)公里/小时自B港向距300公里 的C市驶去,打算在同一天下午16点至晚上21点到达C市.设汽车、摩托艇所需要的时间分别是x小时,y小时.
(Ⅰ)确定x,y应满足的线性约束条件.
(Ⅱ)如果已知所用的经费P=100+3(5-x)+2(8-y)(元),那么v,w分别是多少时走得最经济?此时需要花费多少元?
考点分析:
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设a是实数,f(x)=a-
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(Ⅲ)当f(x)为奇函数时,求f(x)的值域.
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给出下列命题:
①y=1是幂函数;
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x-log
2x的零点有1个;
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的大小关系是b<c<a.
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,
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,
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其中真命题的序号是
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一个棱锥的三视图如图,则该棱锥的体积为
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曲线y=e
x在点(2,e
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