[tex]37. (x^{2} +y^{2} )(x+y)(x-y)=(x^{2} +y^{2} )(x^{2} -y^{2} )=x^{4} -y^{4}\\\\38.(x-2)(x+2)(x^{2} +4)(x^{4} +16)= (x^{2} -4)(x^{2} +4)(x^{4} +16)=(x^{4} -16)(x^{4} +16)=x^{8} -256\\\\39. (n+m)(m-n)=(m+n)(m-n)=m^2-n^2\\(x-y)(x+y)=x^{2} -y^{2}[/tex]