sailboats+and+fish

魏聂阙4637求一些听起来比较干净的歌,安静一点的,不是纯音乐 -
邱鬼别13337458398 ______ 简单生活——苏打绿,falling in love-----Springloll,unique-----lenka,tennis elbow——sky falling ,sailboats-------sky falling,

魏聂阙4637已知数列{an}的前n项和为Sn,且对任意的n属于正整数有an+Sn=n -
邱鬼别13337458398 ______ Sn=n-An ① Sn-1=(n-1)-An-1 ② ①-② An=-An+1+An-12An=(An-1)-1 同时减22(An-1)=(An-1)-1 所以An-1为等比, 公比为2 之后你就会了吧.楼下的我无语了 我是自己一个字一个字打的.

魏聂阙4637数列标准偏差和算术平均值的标准偏差的公式是什么?
邱鬼别13337458398 ______ ∵an与2的算术平均值等于Sn与2的几何平均值,即an+2/2=(2Sn)^(1/2) ∴有an^2+4an+4=8sn ……(1) 在(1)式中分别另n=1、n=2、n=3,且因为an>0, ∴解得a1=2,a2=6,a3=10…… 从而可知数列{an}是等差数列, ∴sn=n(an+2)/2……(2) 把(2)代入(1)式,有(an+2)(an+2-4n)=0 解得an=-2(舍去), an=4n-2. 所以{an}的通项公式为an=4n-2.

魏聂阙4637小学生不学音标,那如何教他们区分a / an 的用法?
邱鬼别13337458398 ______ 一般来说,a,e,i,o,u 打头的单词前面都加an,其它加a就可以了,比如an English book, an article, an Irish, an onion, an UFO

魏聂阙4637设数列{an}的前n项和为Sn,对任意n∈N*满足2Sn=an(an+1),且an≠0 (1)求数列an的通项公式 -
邱鬼别13337458398 ______ 2Sn=an(an+1),2Sn=a(n-1)【a(n-1)+1】,an=Sn-S(n-1) 得2an=an^2(平方)-a(n-1)^2+an-a(n-1).移项,平方的用平方差,因为an≠0,所以两边同除 (an+a(n-1)),得an-a(n-1)=1,又S1=a1,则2a1=a1(a1+1),解得a1=1,所以an=a1+n-1=n

魏聂阙4637有没有适合11到13岁少女听的英文歌?要求舒缓一点,节奏感千万别太强的哪种.英文啊!! -
邱鬼别13337458398 ______ 《heartbeats》Amy Diamond 《a little love》冯曦妤 《Dying In the Sun》The Cranberries 《Suburban Street》Katie Goes to Tokyo 《Sailboats》Sky Sailing 《Crash》Sarah Reeves 《Flightless Bird, American Mout》Iron & Wine 《Try(名扬四...

魏聂阙4637已知数列{an}的前n项和为Sn,又有数列{bn},他们满足b1=a1,且对任意n∈正整数有an+Sn=n,b(n+1)=a(n+1)__
邱鬼别13337458398 ______ an+Sn=n a(n+1)+S(n+1)=n+1 两式相减,得2a(n+1)-an=1 a(n+1)=(1+an)/2,且b(n+1)=a(n+1)--an=1-a(n+1) 对任意n>=2,b(n+1)=1-a(n+1)=1-(1+an)/2=(1-an)/2=bn/2 因此只要n>=2,就有b(n+1)/bn=1/2 对an+Sn=1,令n=1,则a1+S1=1 而S1=a1 因此2*a1=1 a1=1/2 令n=2 a2+S2=22*a2+a1=2 a2=(2-a1)/2=3/4 因此b2=a2-a1=1/4=a1/2=b1/2 也就是说对n=1也有b(n+1)/bn成立 因此{bn}是等比数列

魏聂阙4637艾尔之光官方的歌i was walking..the tree,i was swimming ..the sea,i was flowing ..the air -
邱鬼别13337458398 ______ Sailboats - Sky SailingSailboats wish that they were stars,Floating softly in the skyAmong our dreams that bid goodbyeMoving through transparent space,Drifting through the stratosphereAnd onward till they disappearThese continents from ...

魏聂阙4637正项等差数列an的前n项和为Sn,已知am - 1+am+1 - am^2=0,S2m - 1=38,则m= -
邱鬼别13337458398 ______ 解:设数列an公差为d 则(am-d)+am+d-am^2=0 解得am=0或2 因为数列为正项等差数列 所以am=2 S(2m-1)=(a1+a2m-1)*2m-1/2 a1=am-(m-1)d a2m-1=am+(m-1)d 代入上式得,2am*(2m-1)/2=38 am=2带入,解得m=10

魏聂阙4637give way to 和 make way for 有什么不同?如题 -
邱鬼别13337458398 ______[答案] give way to 让路,让步 The cars gave way to the pedestrians. The motorboats have to give way to the sailboats. make way for 让路给,为...开路 Some fine old buildings have been torn down to make way for an ugly new parking garage.