2018高考答案解析与备考策略

2018高考数学答案解析

1、选择题

（1）函数与导数

1、已知函数f(x)=ax^3-3x^2+1，求f(x)在点P(1,f(1))处的切线方程。

解：因为f'(x)=3ax^2-6x，所以f'(1)=3a-6，又f(1)=a-2，所以切线方程为y-(a-2)=(3a-6)(x-1)，即(3a-6)x-y-4=0。

2、设函数g(x)=x^3-3x^2+2x+m，若g(x)在区间[-1,2]上单调递增，求实数m的取值范围。

解：因为g'(x)=3x^2-6x+2=3(x-1)^2-1\ge -1$，所以g(x)在区间[-1,2]上单调递增等价于g'(x)\ge 0在区间[-1,2]上恒成立，即m\le x^3-3x^2+2x在区间[-1,2]上恒成立，令h(x)=x^3-3x^2+2x，则h'(x)=3x^2-6x+2=3(x-1)^2-1\ge -1$，所以h(x)在区间[-1,2]上单调递增，故h(x)_{min}=h(-1)=0，所以m\le 0。

（2）几何与向量

1、已知点A(2,3)，B(5,4)，C(8,7)，D(6,9)，E(9,6)，F(7,5)，G(4,3)，H(3,2)，I(1,1)，求证：AB//EF。

证明：因为k_{AB}=\dfrac{4}{3}=k_{EF}$，所以AB//EF。

2、已知点O为坐标原点，点A(1,0)，B(0,1)，C(4,5)，求OC边上的高线段AB的长度。

解：因为k_{AB}\cdot k_{OC}=-1$，所以AB边上的高线段OC的斜率k=-k_{AB}=-\dfrac{OA}{OB}=-\dfrac{1}{1}=-1$，又直线AB过点O和A，所以直线AB的方程为y=-x，联立方程组$\begin{cases}y=-x\\ y=5\end{cases}$，得$\begin{cases}x=-5\\ y=5\end{cases}$，所以直线OC上一点M的坐标为$(-5,5)$，又因为OM=√(OA^2+AM^2)=√(12)=√26$，所以AB=OM=√26。

2018高考英语答案解析

1、阅读理解

Passage 1: A recent study shows that people who spend more time on social media are more likely to suffer from depression and anxiety. The study found that people who spent more than two hours a day on social media were twice as likely to suffer from depression and anxiety compared to those who spent less than an hour a day. The study also found that people who use social media to seek validation or attention are more likely to suffer from depression and anxiety. The researchers suggest that people should limit their social media use and focus on building real-life relationships instead.

Passage 2: In recent years, there has been a growing concern about the impact of technology on our mental health. Many experts believe that excessive use of smartphones and social media can lead to feelings of isolation and loneliness, which can contribute to depression and anxiety. However, some experts argue that technology can also be used as a tool for self-care and mental health management. For example, there are now many apps that offer mindfulness exercises and therapy sessions. While it is important to be aware of the potential risks of technology on our mental health, it is also important to recognize its potential benefits.

Passage 3: In today's fast-paced world, stress has become a common problem for many people. Stress can have a negative impact on our physical and mental health, and it can even lead to serious illnesses such as heart disease and diabetes. There are many ways to manage stress, including exercise, relaxation techniques, and counseling. It is important to find healthy coping mechanisms that work for you and to make stress management a priority in your life. Remember that taking care of your mental health is just as important as taking care of your physical health.

2、完形填空

本文主要讲述了一个年轻人如何通过参加志愿者活动找到了自己的兴趣和人生目标，他最初参加志愿者活动是为了积累经验，提高自己的简历，在参加活动的过程中，他逐渐发现自己对帮助他人和改善社会有着浓厚的兴趣，他开始积极参加各种志愿者活动，不仅积累了丰富的经验，还结识了许多志同道合的朋友，最终，他决定将自己的兴趣和才能付诸实践，成立了一个非营利组织，致力于解决社会上的一些重大问题，这个故事告诉我们，通过参加志愿者活动，我们不仅可以为社会做出贡献，还可以找到自己的人生目标和兴趣。

2018高考物理答案解析

1、选择题

（1）力学

1、一个质量为m的物体从静止开始沿光滑的斜面下滑，斜面的高度为h，斜面的倾角为θ，求物体滑到斜面底部时的速度。

解：由能量守恒定律得：mgh=mv^2/2，解得v=\sqrt{2gh}。

2、一个质量为m的物体沿着水平方向以速度v运动，受到一个与速度方向垂直的力F的作用，求物体在力F作用下的加速度。

解：由牛顿第二定律得：F=ma，解得a=F/m=F/mg。

（2）电学

1、一个电阻为R的电阻器与一个电容为C的电容器并联连接在电压为U的电源上，求电流I的大小。

解：由欧姆定律得：I=U/R+U/C。

2、一个电阻为R的电阻器与一个电容为C的电容器串联连接在电压为U的电源上，求电容器两端的电压Uc。

解：由欧姆定律得：Uc=IR=UR/R=U/R，又因为Q=CU=CUc，所以C=Q/Uc=UC/U=R/U，将C代入Uc=IR得：Uc=IR=UR/R=U/R=R/U，所以Uc=R/U。

2018高考化学答案解析

1、选择题

（1）物质的结构与性质

1、下列物质中属于同分异构体的是（）。

A. CO和CO₂ B. H₂O和H₂SO₄ C. CH₄和C₆H₁₂ D. O₂和N₂O

解：同分异构体是指分子式相同而结构不同的化合物，选项A中的CO和CO₂分子式相同，但结构不同，属于同分异构体；选项B中的H₂O和H₂SO₄分子式不同；选项C中的CH₄和C₆H₁₂分子式相同但结构相同；选项D中的O₂和N₂O分子式不同，所以答案是A。

（2）化学反应与平衡

1、在一个封闭的容器中进行如下反应：N₂+3H₂⇌2NH₃，当反应达到平衡时，增加N₂的浓度会使平衡向哪个方向移动？

解：根据勒夏特列原理，当一个化学反应达到平衡时，如果改变某一反应物或生成物的浓度，平衡会向减少这种物质浓度的方向移动，在这个反应中，增加N₂的浓度会使平衡向右移动，即增加NH₃的浓度，所以答案是向右移动。