1）2x²-4x-1=0 ；2）5x+2=3x² ；3）（x-2）（3x-5）=1 ；4）(x+6.8)²+x=10²

1）2x²-4x-1=0 ；2）5x+2=3x² ；3）（x-2）（3x-5）=1 ；4）(x+6.8)²+x=10²

1）2x²-4x-1=0 ；
a=2,b=-4,c=-1
b²-4ac=(-4)²-4x2x(-1)=24
X = (4 ± root 24) / 4
X1 = (2 + radical 6) / 2, X2 = (2-radical 6) / 2
2）5x+2=3x² ；
The original equation can be reduced to 3x & sup2; - 5x-2 = 0
a=3,b=-5,c=-2
b²-4ac=(-5)²-4x3x(-2)=49
X = (5 ± root 49) / 6
x1=2,x2=-1/3
3）（x-2）（3x-5）=1 ；
The original equation can be reduced to 3x & sup2; - 11x + 9 = 0
a=3,b=-11,c=9
b²-4ac=(-11)²-4x3x9=13
X = (11 ± root 13) / 6
X1 = (11 + radical 13) / 6, X2 = (11 radical 13) / 6
4）(x+6.8)²+x=10²
The original equation can be reduced to X & sup2; + 14.6x-53.76 = 0
a=1,b=14.6,c=-53.76
b²-4ac=14.6²-4x1x（-53.76）=428.2
X = (- 14.6 ± root 428.2) / 2
X1 = (- 14.6 + root 428.2) / 2 = 3.0465,
X1 = (- 14.6-radical 428.2) / 2 = 17.6465