Bonsoir
A=x²-2x-3=0
-(-2)±√(-2)²-4x1x(-3)/2x1
2±√4+12/2
2±√16/2
2±4/2
x=2+4/2
x=2-4/4
x=3
x=-1
x₁-1,x₂=3
B=x²-6x+9=0
(x-3)²=0
x-3=0
x=3
C=2x²-3x+5=0
-(-3)±√(-3)²-4x2x5/2x2
3±√9-40/4
3±√-31/4
x∉R
D=2x²-9x+10=0
-(-9)±√(-9)²-4x2x10/2x2
9±√81-80/4
9±√1/4
9±1/4
x=9+1/4
x=9-1/4
x=5/2
x=2
x₁=2,x₂=5/2
E=4x²-8x-5=0
-(-8)±√(-8)²-4x4x(-5)/2x4
8±√64+80/8
8±√144/8
8±12+8
x=8+12/8
x=8-12/8
x=5/2
x=-1/2
x₁=-1/2,x₂=5/2
