解一元二次方程:x方-3x+1=0和2x方+6=7x和3x方-9x+2=0

x方-3x+1=0
x^2-3x+9/4-9/4+1=0
(x+3/2)^2-5/4=0
(x+3/2+√5/2)(x+3/2-√5/2)=0
x=-√5/2-3/2 或 x=√5/2-3/2
2x方+6=7x
2x^2-7x+6=0
(2x-3)(x-2)=0
x=3/2 或 x=2
3x方-9x+2=0
x^2-3x+2/3=0
x^2-3x+9/4-9/4+2/3=0
x^2-3x+9/4-57/36=0
(x-3/2)^2-57/36=0
(x-3/2+√57/6)(x-3/2-√57/6)=0
x=3/2-√57/6 或 x=3/2+√57/6