yz(y+z)+zx(z+x)+xy(x+y)+2xyz
=yz(y+z+x-x)+zx(z+x+x-x)+xy(x+y)+2xyz
=(x-z)(yz+zx)+(x+y)(yz+xy)+2x2z+2xyz
=y(x-z)(x+y)+y(x+z)(x+y)+2xz(x+y)
=(x+y)[y(x-z)+y(x+z)+2xz]
=(x+y)(yx-yz+yx+yz+2xz)
=(x+y)2x(y+z)
Mình sợ sai ấy, bạn kiểm tra lại đi
yz(y+z)+zx(z+x)+xy(x+y)+2xyz
=yz(y+z+x-x)+zx(z+x+x-x)+xy(x+y)+2xyz
=(z-x)(yz+zx)+(x+y)(yz+xy)+2x2z+2xyz
=z(z-x)(x+y)+y(x+z)(x+y)+2xz(x+y)
=(x+y)[z(z-x)+y(x+z)+2xz]
=(x+y)(z2-zx+yx+yz+2xz)
=(x+y)(z2+yx+yz+xz)
=(x+y[z(y+z)+x(y+z)]
=(x+y)(y+z)(z+x)