a^4-b^4=(a^2-b^2)(a^2+b^2)=(a-b)(a+b)(a^2+b^2)
a^4+b^4
=a^4+2a^2b^2+b^4-2a^2b^2
=(a^2+b^2)^2-2a^2b^2
=(a^2-√2ab+b^2)(a^2+√2ab+b^2)
a^4-b^4=(a^2-b^2)(a^2+b^2)=(a-b)(a+b)(a^2+b^2)
a^4+b^4
=a^4+2a^2b^2+b^4-2a^2b^2
=(a^2+b^2)^2-2a^2b^2
=(a^2-√2ab+b^2)(a^2+√2ab+b^2)