x²-4x=2x²-4x+4=6(x-2)²=6x-2=±√6x1=2+√6,x2=2-√6 3x²+5x+1=03x²+5x=-1x²+5x/3=-1/3x²+5x/3+(5/6)²=-1/3+(5/6)²(x-5/6)²=13/36x-5/6=±(√13)/6x1=(5+√13...