由m^2+m-2=0，得m^2+m＝2m^3+2m^2-m+1＝m^3+m^2+m^2-m+1＝m(m^2+m)+m^2-m+1＝2m+m^2-m+1＝m^2+m+1=2+1=3
m可能等于1或-2m=1 m^3+2m^2-m+1=3m=-2 m^3+2m^2-m+1=3
