不好意思,刚看错了
3x^2+4xy-y^2
=3(x^2+xy*4/3-y^2*1/3)
=3[(x^2+2*2/3*xy+4/9y^2)-y^2/3-4/9y^2]
=3[(x+2/3y)^2-7/9y^2]
=3(x+2/3y+√7/3y)(x+2/3y-√7/3y)
=3[x+(2+√7)/3y][x+(2-√7)/3y]
不好意思,刚看错了
3x^2+4xy-y^2
=3(x^2+xy*4/3-y^2*1/3)
=3[(x^2+2*2/3*xy+4/9y^2)-y^2/3-4/9y^2]
=3[(x+2/3y)^2-7/9y^2]
=3(x+2/3y+√7/3y)(x+2/3y-√7/3y)
=3[x+(2+√7)/3y][x+(2-√7)/3y]