x²+(m+2)x+(2m+1)=0判别式=（m+2）^2-4(2m+1) =m^2+4m+4-8m-4 =m^2-4m2.方程两根互为相反数x1+x2=-(m+2)/2=0m=-2原方程x^2-3=0x1=根号3，x2=-根号3
