x²-5x+2=0
x²-5x+25/4=25/4-2
(x-5/2)²=17/4
x-5/2=±(√17)/2
x=(5±√17)/2
x²=6x+1
x²-6x+9=1+9
(x-3)²=10
x-3=±√10
x=3±√10
2x²-3x=0
x²-3x/2+9/16=9/16
(x-3/4)²=9/16
x-3/4=±3/4
∴x1=0
x2=3/2
3x²+6x+5=0
△=36-4*3*5=36-60<0
∴原方程无解
0.2x²-0.1=0.4x
2x²-4x-1=0
x²-2x=1/2
x²-2x+1=1/2+1
(x-1)²=3/2
x-1=±√(3/2)
x=1±1/2√6
√2x-2=2x²
2x²-√2x+2=0
△=(√2)²-4*2*2=2-16<0
∴原方程无解