\(a,=\left(x-y\right)\left(x+y\right)-\left(x+y\right)=\left(x+y\right)\left(x-y-1\right)\\ b,=\left(x-y\right)^2-z^2=\left(x-y-z\right)\left(x-y+z\right)\\ c,=\left(2x+1\right)^2-y^2=\left(2x+1-y\right)\left(2x+1+y\right)\\ d,=\left(x+y\right)\left(x^2-xy+y^2\right)-\left(x+y\right)\\ =\left(x+y\right)\left(x^2-xy+y^2-1\right)\\ e,=3\left(x^2-2xy+y^2-4z^2\right)\\ =3\left[\left(x-y\right)^2-4z^2\right]=3\left(x-y-2z\right)\left(x-y+2z\right)\\ f,=\left(x+y\right)^2-25=\left(x+y-5\right)\left(x+y+5\right)\\ g,=\left(x+2\right)^2-y^2=\left(x+y-2\right)\left(x-y+2\right)\\ h,=3\left(x^2+2xy+y^2-z^2\right)=3\left[\left(x+y\right)^2-z^2\right]\\ =3\left(x+y-z\right)\left(x+y+z\right)\\ i,=\left(x-y\right)^2-\left(z-t\right)^2=\left(x-y-z+t\right)\left(x-y+z-t\right)\)
