Ta có: \(\left(x+y\right)\left(y+z\right)\left(z+x\right)+xyz=x^2y+xy^2+xyz+y^2z+yz^2+xyz+xz^2+x^2x+xyz\)
\(=xy\left(x+y+z\right)+yz\left(x+y+z\right)+zx\left(x+y+z\right)=\left(x+y+z\right)\left(xy+yz+zx\right)\)
\(x^2-y^2+10x-6y+16=\left(x^2+10x+25\right)-\left(y^2+6y+9\right)\)
\(=\left(x+5\right)^2-\left(y+3\right)^2=\left(x+y+8\right)\left(x-y+2\right)\)
\(x^2\left(y-z\right)+y^2\left(z-x\right)+z^2\left(x-y\right)=x^2\left(y-z\right)+yz\left(y-z\right)-x\left(y-z\right)\left(y+z\right)\)
\(=\left(y-z\right)\left(x^2+yz-xy-xz\right)=\left(y-z\right)\left(x-y\right)\left(z-x\right)\)