已知数列:1,2,2,4,3,6,4,8,5,10,...,若将第一个数记为A1,第2个数记为A2,...,第n个数记为An,则有Am + An =129,An+2Am=138,那么,n= ( )计算:2005a------- =2005(a+b)的值等于( )b 设一列数A1、A2、A3、...’A100
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![已知数列:1,2,2,4,3,6,4,8,5,10,...,若将第一个数记为A1,第2个数记为A2,...,第n个数记为An,则有Am + An =129,An+2Am=138,那么,n= ( )计算:2005a------- =2005(a+b)的值等于( )b 设一列数A1、A2、A3、...’A100](/uploads/image/z/7205182-70-2.jpg?t=%E5%B7%B2%E7%9F%A5%E6%95%B0%E5%88%97%EF%BC%9A1%2C2%2C2%2C4%2C3%2C6%2C4%2C8%2C5%2C10%2C...%2C%E8%8B%A5%E5%B0%86%E7%AC%AC%E4%B8%80%E4%B8%AA%E6%95%B0%E8%AE%B0%E4%B8%BAA1%2C%E7%AC%AC2%E4%B8%AA%E6%95%B0%E8%AE%B0%E4%B8%BAA2%2C...%2C%E7%AC%ACn%E4%B8%AA%E6%95%B0%E8%AE%B0%E4%B8%BAAn%2C%E5%88%99%E6%9C%89Am+%2B+An+%3D129%2CAn%2B2Am%3D138%2C%E9%82%A3%E4%B9%88%2Cn%3D+%EF%BC%88+%EF%BC%89%E8%AE%A1%E7%AE%97%EF%BC%9A2005a-------+%3D2005%EF%BC%88a%2Bb%EF%BC%89%E7%9A%84%E5%80%BC%E7%AD%89%E4%BA%8E%EF%BC%88+%EF%BC%89b+%E8%AE%BE%E4%B8%80%E5%88%97%E6%95%B0A1%E3%80%81A2%E3%80%81A3%E3%80%81...%E2%80%99A100)
已知数列:1,2,2,4,3,6,4,8,5,10,...,若将第一个数记为A1,第2个数记为A2,...,第n个数记为An,则有Am + An =129,An+2Am=138,那么,n= ( )计算:2005a------- =2005(a+b)的值等于( )b 设一列数A1、A2、A3、...’A100
已知数列:1,2,2,4,3,6,4,8,5,10,...,若将第一个数记为A1,第2个数记为A2,...,第n个数记为An,则有Am + An =129,An+2Am=138,那么,n= ( )
计算:
2005a
------- =2005(a+b)的值等于( )
b
设一列数A1、A2、A3、...’A100中任意三个相邻数之和是37,已知A2=25,A9=2x,A99=3-x,那么A100= ( )
会做的都做一下阿,
已知数列:1,2,2,4,3,6,4,8,5,10,...,若将第一个数记为A1,第2个数记为A2,...,第n个数记为An,则有Am + An =129,An+2Am=138,那么,n= ( )计算:2005a------- =2005(a+b)的值等于( )b 设一列数A1、A2、A3、...’A100
1、观察此数列知:A1=1 A3=2 A5=3 那么An=(n+1)/2
A2=2 A4=4 A6=6 那么Am= m
所以:Am + An =129,An+2Am=138 可以得出Am=9 那么An=120
=120 n=239
2、看不懂你的题目是什么意思!
3、任意三个相邻数之和是37,由这句可以得出 :
A1+A2+A3=37 A2+A3+A4=37 A3+A4+A5=37 A4+A5+A6=37
可知:A1=A4=A7=A10= …… A97=A100
A2=A5=A8=A11= …… A98
A3=A6=A9=A12= …… A99
已知A2=25,A9=2x,A99=3-x 2x=3-x x=1
A2=25 A3=A9=A99=2 那么:A1=A100=10