Verified answer

[tex]\displaystyle\bf\\1)\\\\16x^{2} -y^{4}=(4x)^{2}-(y^{2})^{2} =(4x-y^{2})\cdot(4x+y^{2})\\\\\\2)\\\\x^{2} -5x+5y-y^{2}=(x^{2} -y^{2})-(5x-5y)=\\\\=(x-y)\cdot(x+y) -5\cdot(x-y)=(x-y)\cdot(x+y-5)[/tex]