$\displaystyle \begin{array}{{>{\displaystyle}l}} h) \ x^{2} -2xy+y^{2} -z^{2}\\ =( x-y)^{2} -z^{2}\\ =( x-y-z)( x-y+z) \ \\ i) \ x^{2} -xy+x-y\\ =x( x-y) +( x-y)\\ =( x-y)( x+1) \ \\ j) \ x^{2} -2x+2y-xy\\ =x( x-2) -y( x-2) \ \\ =( x-2)( x-y) \ \\ k) \ 2x-2y-x^{2} +2xy-y^{2}\\ =2( x-y) -\left( x^{2} -2xy+y^{2}\right)\\ =2( x-y) -( x-y)^{2}\\ =( x-y)( 2-x+y) \ \\ l) \ 3x+3y-x^{2} -2xy-y^{2}\\ =3( x+y) -( x+y)^{2}\\ =( x+y)( 3-x-y) \ \\ m) \ x^{2} +2xy+y^{2} -z^{2}\\ =( x+y)^{2} -z^{2}\\ =( x+y-z)( x+y+z) \ \\ n) \ x^{2} +xy+x+y\\ =x( x+y) +( x+y)\\ =( x+y)( x+1) \ \end{array}$
