已选分类
理学数学
单选题How many two-digit numbers can be written using digits 0 through 6 if no digit can be repeated and 0 cannot be the first digit?
单选题设f'(x0)=f"(x0)=0，(x0)＞0，则下列选项中正确的是______。A.f'(x0)是f'(x)的极大值B.f(x0)是f(x)的极大值C.f(x0)是f(x)的极小值D.点(x0，f(x0))是曲线y=f(x)的拐点
单选题若向量组α，β，γ线性无关，α，β，δ线性相关，则______。
A.α必可由β，γ，δ线性表示
B.β必不可由α，γ，δ线性表示
C.δ必可由α，β，γ线性表示
D.δ必不可由α，β，γ线性表示
单选题If the value of a piece of property decreases by 10 percent while the tax rate on the property increases by 10 percent, what is the effect on the taxes?
单选题WhatistheperimeterofpentagonVWXYZshownabove?(A)53(B)58(C)60(D)66(E)70
单选题In1960,thenumberofstudentsenrolledatacollegewas500.In1980,thenumberofstudentsenrolledatthecollegewastimesasgreatasthatin1960.Whatwasthenumberofstudentsenrolledatthecollegein1980?
单选题If a certain chemical costs $50 for 30 gallons, then how many gallons of the chemical can be purchased for $625? (A) 12.5 (B) 24 (C) 325 (D) 375 (E) 425
单选题设x4+ax3-bx+2能被x2+3x+2整除，则( ). A．a=-6，b—3 B．a=-6，b=-3 C．a=6，b=3 D．a=6，b=-3 E．a=3，b=-6
单选题
单选题a，b，c，是不全相等的任意实数，若x=a2-bc，y=b2-ac，z=c2-ab，则x，y，z为( )． A．都大于0 B．至少有一个大于0 C．至少有一个小于0 D．都不小于0 E．都小于0
单选题Abusinessfirmreducesthenumberofhoursitsemployeesworkfrom40hoursperweekto36hoursperweekwhilecontinuingtopaythesameamountofmoney.Ifanemployeeearnedxdollarsperhourbeforethereductioninhours,howmuchdoesheearnperhourunderthenewsystem?
单选题How many minutes will it take to completely fill a water tank with a capacity of 3,750 cubic feet if the water is being pumped into the tank at the rate of 800 cubic feet per minute and is being drained out of the tank at the rate of 300 cubic feet per minute?
单选题The Binary Ice Cream Shoppe sells two flavors, vanilla and chocolate. On Friday, the ratio of vanilla cones sold to chocolate cones sold was 2 to 3. If the store had sold 4 more vanilla cones, the ratio of vanilla cones sold to chocolate cones sold would have been 3 to 4. How many vanilla cones did the store sell on Friday?
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单选题Intheprecedingfigure,ifl1∥l2,whatisthevalueofx?
单选题设a，b，c三数成等差数列，若x，y分别是a，b和b，c的等比中项，则x2+y2=______． A．2a2 B．b2 C．2b2 D．c2
单选题Candy hearts were marked down from 30% to 50% on Valentine's Day. The following day, candy hearts were marked down an additional 25%. What was the lowest cost of a candy heart that originally sold for $ 28? (A) $7 (B) $12.60 (C) $14 (D) $15.40 (E) $21
单选题设，则x=1，Δx=0.03时，dy=______．A．0.01B．0.03C．0.01dxD．0.03dx
单选题如图，在直角三角形ABC区域内部有座山，现计划从BC边上的某点D开凿一条隧道到点A，要求隧道长度最短，已知AB长为5km，AC长为12km，则所开凿的隧道AD的长度约为( )．
单选题已知f(x)在x=0的某个邻域内连续，且，则f(x)在点x=0处______。A.不可导B.可导且f'(x)≠0C.取得极大值D.取得极小值