根据韦达定理知x1+x2=-k,于是知x1=-k-x2.由x1+2*x2^2=k知,2*x2^2=k-x1=k-(-k-x2)=2k+x2.又x2是方程x^2+kx+k+1=0的根,所以x2^2+k*x2+k+1=0,即2*x2^2=-2(k+1)-2k*x2.所以2k+x2=-2(k+1)-2k*x2,知(2k+1)*x2=-4k-2=-2(2k+...