1.2x²-4x=1
x²-2x-1/2=0
x²-2x+1-1-1/2=0
（x-1）²=3/2
x-1=±√6/2
x1=1+√6/2
x2=1-√6/2
2.x²-3x=0
x²-3x+9/4-9/4=0
（x-3/2）²=9/4
x-3/2=±3/2
x1=3,x2=0
3.1/4x²-x+1=0
x²-4x+4=0
（x-2）²=0
x-2=0
x=2
4.2x²=6x-5
2x²-6x+5=0
x²-3x+5/2=0
x²-3x+9/4-9/4+5/2=0
（x-3/2)²=-1/4
无解.