2018年七年级英语周报答案

21.(本小题满分12分)(1)由f(x)= a cos x-e得f(x)=- asin-e则切线方程的斜率k=f(0)=-1解得b=1又切点坐标为(0,a-1),则a-1=-÷=-2,解得a=-1.(4分n)令f(x)= -asin x-e'=0,故方程-0m+z上有两个不同实数解6即直线y=-a与函数g(xmnr的图象有两个不同的交点8r) e( sin x-cosr). v2esinr-zsin x则当x∈时,g(x)<0,当x64g(x)>0函数g(x)在兀,z上单调递减,在(x,z上单调递增6’43号号要使直线y=-a与函数g(x)的图象有两个不同的交点则√2e<-a≤2e6,∴-2e≤a<-2即实数a的取值范围是-2e,-V(12分

One possible versionDear Peter,Im very glad to learn that a prevention ofCOVID-19 activity will be held in your school. It'sagood opportunity for you to learn more about defendingagainst virus and protecting yourself.First a lecture about prevention of COVID-19 is agood choice, As the virus has spread all over theworld, causing many deaths, some protection measuresshould ensure everyone to know. For example, do notgo to places where people gather. Try to reduce thecontact with the people who come back from theepidemic city and prevent the spread of the epidemicsituation.Additionally, holding a competition aboutprevention of COVID-19 can also arouse peopleinterest, which is very helpful in learning knowledgerelated to COVID-19. What's more, posters aboutprotecting ourselves during COVID-19 are surelywelcome.I hope my suggestions will be of great help toyouYoursLi Hua

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