\(x^4y^4+64=x^4y^4+16x^2y^2+64-16x^2y^2=\left(x^2y^2+8\right)^2-16x^2y^2=\left(x^2y^2-4xy+8\right)\left(x^2y^2+4xy+8\right)\)
\(x^8+x+1=x^8-x^2+\left(x^2+x+1\right)=x^2\left(x^6-1\right)+\left(x^2+x+1\right)=x^2\left(x^3-1\right)\left(x^3+1\right)+\left(x^2+x+1\right)=x^2\left(x-1\right)\left(x+1\right)\left(x^2+x+1\right)\left(x^2-x+1\right)+x^2+x+1=\left(x^2+x+1\right)\text{[}x^2\left(x+1\right)\left(x-1\right)\left(x^2-x+1\right)+1\text{]}\)
\(g,tach:x^2+x+1\)
\(x^4+4y^4=x^4+4x^2y^2+4y^4-4x^2y^2=\left(x^2+2y^2\right)^2-\left(2xy\right)^2=\left(x^2-2xy+2y^2\right)\left(x^2+2xy+2y^2\right)\) \(4x^4+1=4x^4+4x^2+1-4x^2=\left(2x^2+1\right)^2-\left(2x\right)^2=\left(2x^2+2x+1\right)\left(2x^2-2x+1\right)\)
\(a^2-b^2-2x\left(a-b\right)=\left(a+b\right)\left(a-b\right)-2x\left(a-b\right)=\left(a+b-2x\right)\left(a-b\right)\)
\(a^2-b^2-2x\left(a+b\right)=\left(a-b\right)\left(a+b\right)-2x\left(a+b\right)=\left(a-b-2x\right)\left(a+b\right)\)