х^2-4х-5=0
х^2+7х+12=0
х^2-11х+10=0
2х^2-3х+1=0

1)x²-4x-5=0x1+x2=4 U x1*x2=-5x1=-1 U x2=52)x²+7x+12=0x1+x2=-7 U x1*x2=12x1=-4 U x2=-33)x²-11x+10=0x1+x2=11 U x1*x2=10x1=1 U x1*x2=104)2x²-3x+1=0D=9-8=1x1=(3-1)/4=0,5 U x2=(3+1)/4=1