4x²-12x=3
4[x²-3x+﹙3/2﹚²-﹙3/2）²]=3
4(x-3/2)²-9=3
4(x-3/2)²=12
( x-3/2)²=3
x-3/2=±√3
∴x1=3/2+√3 x2=3/2-√3