已知m是方程x2-2008X+1=0的一个根,求代数式2m2-4015m-2+2008/(m2+1)的解
问题描述:
已知m是方程x2-2008X+1=0的一个根,求代数式2m2-4015m-2+2008/(m2+1)的解
答
m是方程x^2-2008x+1=0
则m^2-2008m+1=0
所以可化为
2m^2-4016m+2=0,即2m^2-4015m=m-2,
或m^2+1=2008m
或m+1/m=2008
所以
2m^2-4015m-2+2008/(m^2+1)
=m-2-2+2008/(2008m)
=m-4+1/m
=m+1/m-4
=2008-4
=2004
答
由题意,把根a代入x2-2008x+1=0,可得:a2-2008a+1=0,
∴a2-2007a=a-1,a2+1=2008a;
∴ =a-1+ =a+ -1
= -1= -1
=2008-1,
=2007
答
将m代入方程得m^2-2008m+1=0 得m^2+1=2008m
2m^2-4015m+2008/(m^2+1)-2=2m^2-4016m+2+m-4+2008/(m^2+1)
=2(m^2-2008m+1)+m-4+2008/2008m =m+1/m-4