x1+x2=2k+3x1x2=k²1/x1+1/x2=1(x1+x2)/x1x2=1(2k+3)/k²=1k²-2k-3=0(k-3)(k+1)=0k1=3 ;k2=-1
1/x1+1/x2=1 则x1+x2=x1*x2由根与系数间关系x1+x2=2k+3，x1*x2=k^2所以2k+3=k^2即k^2-2k-3=0所以k=3或k=-1
