(m²-1)x²+(m-1)x+8=0
是一元一次方程,m-1≠0,即m≠1
(m²-1)=0,m=-1
(-1-1)x+8=0
-2x+8=0
x=4
代数式2(x-m)(x+2m)-3m+2
=2(4+1)(4-2)+3+2
=10*2+5
=25