Δ=m²-8m+4≥0;(m-4)²≥12;m-4≥2√3或m-4≤-2√3；m≥4+2√3或m≤4-2√3;x1+x2=m;x1x2=2m-1;∴x1²+x2²=(x1+x2)²-2x1x2=m²-4m+2=23;∴m²-4m-21=0;(m-7)(m+3)=0;m=7或m=-3；∴m=-...