3X²+4X-1=0
X²+(4/3)X-(1/3)=0
x²＋4/3×＋(4/3*1/2)^2-(4/3*1/2)^2-1/3=0
（x+4/3*1/2)^2-(4/3*1/2)^2-1/3=0
(x+2/3)^2-4/9-1/3=0
(x+2/3)^2=7/9
x+2/3=±√7/3
x=±√7/3－2/3
X1=√7-2/3
X2=-√7-2/3