x1+x2=-2k
x1x2=k²-2k+1
x1²+x2²=4
(x1+x2)²-2x1x2=4
(-2k)²-2(k²-2k+1)=4
4k²-2k²+4k-2=4
2k²+4k-6=0
k²+2k-3=0
(k+3)(x-1)=0
k1=-3 k2=1
x1+x2=-2k
x1x2=k²-2k+1
x1²+x2²=4
(x1+x2)²-2x1x2=4
(-2k)²-2(k²-2k+1)=4
4k²-2k²+4k-2=4
2k²+4k-6=0
k²+2k-3=0
(k+3)(x-1)=0
k1=-3 k2=1