用韦达定理先判断△是否大于等于零经判断△≥0则x1+x2=2/3；x1*x2=-4/3(x1+x2)^2=x1^2+x2^2+2*x1*x2=4/9x1^2+x2^2=35/181.1/x1+1/x2=(x1+x2)/x1*x2=-1/22.x2/x1+x1/x2=(x1^2+x2^2)/x1*x2=-35/243.(x1-x2)^2=(x1+x2)^2-4*x1*x2=31/9
