同志们,大侠们.快帮小女解一道数学题...谢谢啦,要过程

m,n是方程x的平方减2x减1的两个实数根
m^2-2m-1=0
n^2-2n-1=0
m^2=2m+1
n^2=2n+1
n+m=2
mn=-1
3m^2-n^2-8m+1
=3(2m+1)-(2n+1)-8m+1
=6m+3-2n-2-8m+1
=-2m-2n+2
=-2(m+n)+2
=-2*2+2
=-2