已选分类
理学数学
单选题A figure that can be folded over along a straight line so that the result is two equal halves which are then lying on top of one another with no overlap is said to have a line of symmetry. Which of the following figures has only one line of symmetry?
单选题Last year, an appliance store sold an average (arithmetic mean) of 42 microwave ovens per month. In the first 10 months of this year, the store has sold an average (arithmetic mean) of only 20 microwaves per month. What was the average number of microwaves sold per month during the entire 22-month period? (A) 21 (B) 30 (C) 31 (D) 32 (E) 44
单选题若F(x)为f(x)的一个原函数，则∫xf'(x)dx=______。
A.xF'(x)-f(x)+C
B.xF'(x)-F(x)+C
C.xf'(x)-F(x)+C
D.xf'(x)-f(x)+C
单选题设A是5×6矩阵，而且A的行向量线性无关，则______。A．A的列向量线性无关B．线性方程组AX=B的增广矩阵的行向量线性无关C．线性方程组AX=B的增广矩阵的任意4个列向量线性无关D．线性方程组AX=B有唯一解
单选题设函数在(-∞，+∞)上连续，且，则应有______。A.k＜0，c＜0B.k＞0，c＞0C.k≤0，c＞0D.k≥0，c＜0
单选题设A、B为n阶方阵，且B=B2，A=E+B，则A-1=______。A．(3E-A)B．B-1C．2ED．-B-1
单选题Somebody bought some pencils and rubbers in a shop. What's the price for each pencil? (1)he paid 215 cents for 2 pencils and 3rubbers (2)he should have bought 8 pencils and12 rubbers if he paid 860 cents. (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
单选题During a sale at an office supply store, for every box of paper clips purchased for 15 cents, a second box can be purchased for 4 cents. How many boxes of paper clips did Paul buy if he spent 91 cents on boxes of paper clips?
单选题如图，长方形ABCD的两条边长分别为8m和6m，四边形OEFG的面积是4m2，则阴影部分的面积为( )．
单选题
单选题设函数，则______。A.x=0是f(x)的第一类间断点B.x=0是f(x)的第二类间断点C.x=0是f(x)的连续点D.x=0是f(x)的可导点
单选题
单选题设曲线水平渐近线的条数为a，铅直渐近线的条数为b，则______。A.a=0，b=1B.a=1，b=0C.a=1，b=1D.a=2，b=1
单选题AfterreadingofhisbiologyhomeworkonMondaynight,BerniereadofhisremaininghomeworkonTuesdaynight.WhatfractionofhisoriginalhomeworkwouldBerniehavetoreadonWednesdaynighttocompletehisbiologyassignment?
单选题
单选题某批商品样式分A和B两种，形状有大小两种，大的占40%，问B所占的比例是多少? (1)大中有30%A (2)小中有40%A (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
单选题若L1的斜率小于0，问其在y轴上的截距(intercept)是否为正? (1)L1过点(4, 5) (2)在x轴的intercept为正。 (A) 条件(1)充分，但条件(2)不充分． (B) 条件(2)充分，但条件(1)不充分． (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分． (D) 条件(1)充分，条件(2)也充分． (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．
单选题设函数f(x)可导，f(0)=0，f'(0)=1，，则______。A.k=2，λ=2B.k=3，λ=3C.k=3，λ=2D.k=4，λ=1
单选题
单选题Paul is standing 180 yards due north of point P, Franny is standing 240 yards due west of point P. What is the shortest distance between Franny and Paul? (A) 60 yards (B) 300 yards (C) 420 yards (D) 900 yards (E) 9,000 yards