18x²-9x=65 配方
(18x²-9x)×1/18=65×1/18
x²-x/2=65/18
x²-x/2+(1/4)²=65/18+(1/4)²
(x-1/4)²=529/144
x-1/4=±√(529/144)
x-1/4=±23/12
x-1/4=23/12或x-1/4=-23/12
x=13/6或x= -5/3