ab(c^2 -d^2)+cd(a^2 -b^2)
=abc^2+a^2cd-abd^2-b^2cd
=ac(bc+ad)-bd(ad+bc)
=(ac-bd)(ad+bc)
x^5+x+1
=x^5-x^2+x^2+x+1
=x^2(x^3-1)+(x^2+x+1)
=x^2(x-1)(x^2+x+1)+(x^2+x+1)
=(x^3-x^2)(x^2+x+1)+(x^2+x+1)
=(x^3-x^2+1)(x^2+x+1)
ab(c^2 -d^2)+cd(a^2 -b^2)
=abc^2+a^2cd-abd^2-b^2cd
=ac(bc+ad)-bd(ad+bc)
=(ac-bd)(ad+bc)
x^5+x+1
=x^5-x^2+x^2+x+1
=x^2(x^3-1)+(x^2+x+1)
=x^2(x-1)(x^2+x+1)+(x^2+x+1)
=(x^3-x^2)(x^2+x+1)+(x^2+x+1)
=(x^3-x^2+1)(x^2+x+1)