a) Ta có: \(x^4y^4+x^2y^2+1\)
\(=\left(x^4y^4+2x^2y^2+1\right)-x^2y^2\)
\(=\left(x^2y^2+1\right)^2-\left(xy\right)^2\)
\(=\left(x^2y^2-xy+1\right)\left(x^2y^2+xy+1\right)\)
c) \(4x^4+1\)
\(=\left(4x^4+4x^2+1\right)-4x^2\)
\(=\left(2x^2+1\right)^2-\left(2x\right)^2\)
\(=\left(2x^2-2x+1\right)\left(2x^2+2x+1\right)\)
x4y4 + x2y2 + 1
= ( x4y4 + 2x2y2 + 1 ) - x2y2
= ( x2y2 + 1 )2 - ( xy )2
= ( x2y2 - xy + 1 )( x2y2 + xy + 1 )
4x4 + 1
= ( 4x4 + 4x2 + 1 ) - 4x2
= ( 2x2 + 1 )2 - ( 2x )2
= ( 2x2 - 2x + 1 )( 2x2 + 2x + 1 )