Question

factorize it please​

Answer 1

$(x+y)^4-(x-y)^4=\\((x+y)^2-(x-y)^2)((x+y)^2+(x-y)^2)=\\(x+y-(x-y))(x+y+x-y)(x^2+2xy+y^2+x^2-2xy+y^2)=\\(x+y-x+y)\cdot 2x \cdot (2x^2+2y^2)=\\2y\cdot 2x\cdot 2(x^2+y^2)\\8xy(x^2+y^2)$