Question

m,n为方程x^2+2x-1=0的两个实数根,问3m^2-n^2-8m+1=?

Answer 1

m.n是方程X^2-2X-1=0

利用根与系数关系

m+n=2

mn=-1

m是方程的根 则

m^2-2m-1=0

8m=4m^2-4

3m^2-n^2-8m+1

=3m^2-n^2-4m^2+4+1

=-(m^2+n^2)+5

=-[(m+n)^2-2mn]+5

=-(4+2)+5

=-1

原题有误~~,一次项系数应为2