Processing Math: Done
To print higher-resolution math symbols, click the
Hi-Res Fonts for Printing button on the jsMath control panel.

jsMath
發新話題
打印

95中一中

我把八神庵回覆的內容詳細打下來好了。
(我都打完字了,不PO上來也浪費。= =)


計算第 3 題:

設方程式 x52x4+x3+1=0 之五根為 x1x2x3x4x5,設 aij=1+xixj (若 i=j),aij=xixj (若 i=j ),

試求 a11a21a31a41a51a12a22a32a42a52a13a23a33a43a53a14a24a34a44a54a15a25a35a45a55 之值?



解答:

x1=ax2=bx3=cx4=dx5=e,則所求如下,

1+a2abacadaeab1+b2bcbdbeacbc1+c2cdceadbdcd1+d2deaebecede1+e2

=1+a2a2a2a2a2b21+b2b2b2b2c2b21+c2c2c2d2d2d21+d2d2e2e2e2e21+e2


=1+a2+b2+c2+d2+e21+a2+b2+c2+d2+e21+a2+b2+c2+d2+e21+a2+b2+c2+d2+e21+a2+b2+c2+d2+e2b21+b2b2b2b2c2b21+c2c2c2d2d2d21+d2d2e2e2e2e21+e2


=1+a2+b2+c2+d2+e211111b21+b2b2b2b2c2b21+c2c2c2d2d2d21+d2d2e2e2e2e21+e2


=1+a2+b2+c2+d2+e210000b21000c20100d20010e20001

=1+a2+b2+c2+d2+e2

=1+a+b+c+d+e22ab+ac+ad+ae+bc+bd+be+cd+ce+de 

=1+2221

=3


證明對任意正整數 n,恆有
1+81+127+164++1n3125
.


證明:

先觀常一般項,
1n31n3n=1n1nn+1=211n1n1nn+1n1 


所以,

1+81+127+164++1n31+1123+1234++1n1nn+1 

=1+21112123+123134++1n1n1nn+1=1+4112nn+145 


故,對任意正整數 n1+81+127+164++1n3125 恆成立.

多喝水。

TOP

發新話題
最近訪問的版塊