（1）2x²—3x—1=0
x²-3x/2=1/2
x²-3x/2+9/16=17/16
(x-3/4)²=17/16
x-3/4=±√17/4
x=3/4+√17/4 x=3/4-√17/4
（2）3m²—m—5=0
m²-m/3=5/3
m²-m/3+1/36=61/36
(m-1/6)²=61/36
m-1/6=±√61/6
m=1/6+√61/6 m=1/6-√61/6
（3）4x²—1=6x
x²-3x/2=1/4
x²-3x/2+9/16=13/16
(x-3/4)²=13/16
x-3/4=±√13/4
x=3/4+√13/4 x=3/4-√13/4