x² + 6x + 8 = 0
D= p²-4q=36-32=4 > 0
x1=-6+2/2=-2
x2=-8/2=-4
x² — 3x — 1,75 = 0
D=9+7=16 > 0
x1= 3+4/2=3,5
x2=3-4/2=-1/2=-0,5
x² — 6x + 6 = 0
D=36-24=12 > 0
x1=6+_/4•3/2=6+2_/3/2=3+_/3/2=3+_/3
x2=3-_/3
x² — 3x + 1 = 0
D=9-4=5
x1=3+_/5/2
x2=3-_/5/2
x² + 8x + 15 = 0
D=64-60=4
x1=-8+2/2=-3
x2=-8-2/2=-5