x²+(2-m)x-1=0所以x1+x2=m-2x1x2=1所以x1²+x2²=(x1+x2)²-2x1x2=m²-4m+4-2=7m²-4m-5=0(m-5)(m+1)=0m=5,m=-1△>=0(m-2)²-4>=0符合所以m=5,m=-1