2x²+3x-2=0
x²+3x/2-1=0
(x+3/4)²-9/16-1=0
(x+3/4)²=25/16
(x+3/4)²=(5/4)²
x1+3/4=5/4,x1=1/2;
x2+3/4=-5/4,x2=-2;
3x²-2x-5=0
x²-2x/3-5/3=0
(x-1/3)²-1/9-15/9=0
(x-1/3)²=16/9
(x-1/3)²=(4/3)²
x1-1/3=4/3,x1=5/3;
x2-1/3=-4/3,x2=-1;
x²+2ax+a²-b²=0,
(x+a)²=b²
x1+a=b,x1=b-a;
x2+a=-b,x2=-b-a;
x²+px+q=0
(x+p/2)²-p²/4+q=0
(x+p/2)²=(p²-4q)/4
x1+p/2=[√(p²-4q)]/2,x1=[-p+√(p²-4q)]/2;
x2+p/2=-[√(p²-4q)]/2,x2=[-p-√(p²-4q)]/2;
p²-4q>=0;