令x^2-5x+3=0用求根公式求到x1=(5+√13)/2 ,x2=(5-√13)/2所以x2-5x+3分解为(x-(5+√13)/2)(x-(5-√13)/2)
x^2-5x+3=(x-5/2)^2-13/4=[x-(5+√13)/2][x+(√13-5)/2]
x2—5x+3=(x-5/2)^2-25/4+3=(x-5/2)^2-(√13/2)^2=(x-5/2-√13/2)(x-5/2+√13/2)