5x2-6x-8=0 delta=9+40=49 x=3+7/5=2 x2=3-7/5=-4/5
x2+14x+49=0 delta=49-49=0 x=-7+0=-7
2x2+8x-42=0 x2+4x-21=0 delta=4+21=25 x=-2+5=3 x2=-2-5=-7
3x2-2x-8=0 delta=1+24=25 x1=1+5/3=2 x2=1-5/3=-4/3
16x2-16x-5=0 delta=64+80=144 x1=8+12/16=1 x2=8-12/16=-1/4
5x2+14x-24=0 delta=49+120=169 x1=-7+13/5=6/5 x2=-7-13/5=-4