用配方法解方程:
x²+4x=0
x²+4x+4=4
(x+2)²=4
x+2=±√4
x+2=±2
x+2=2 或 x+2=-2
x1=0 ,x2=-4
3x²-5x=-2 方程两边同时除以3
x²-(5/3)x=-2/3
x²-(5/3)x+(5/6)²=-2/3+(5/6)²
[x -(5/6) ]²=1/36
x -(5/6)=±√(1/36)
x -(5/6)=±1/6
x -(5/6)=1/6 或 x-(5/6)=-1/6
x1=1 ,x2=2/3
2x²+3x=-1 方程两边同时除以2
x²+(3/2)x=-1/2
x²+(3/2)x+(3/4)²=-1/2+(3/4)²
[x +(3/4)]²=1/16
x +(3/4)=±√(1/16)
x +(3/4)=±1/4
x +(3/4)=1/4 或 x+(3/4)=-1/4
x1=-1/2 ,x2=-1