X²+3x+2=0
D=9-8=1
х₁=(-3+1)/2=-1 х₂=(-3-1)/2=-2
x²-7x+12=0
D=49-48=1
х₁=(7+1)/2=4 х₂=(7-1)/2=3
3x²+5x-2=0
D=25+24=7²
х₁=(-5+7)/6=1/3 х₂=(-5-7)/6=-2
9x²-6x+1=0
D=36-36=0
х₁х₂=6/18=1/3
5x²-14x+8=0
D=196-160=6²
х₁=(14+6)/10=2 х₂=(14-6)/10=0,8
9x²-12x+4=0
D=144-144=0
х₁=х₂=12/18=2/3