b)\(x^2y+xy^2-x-y\)
\(=xy\left(x+y\right)-\left(x+y\right)\)
\(=\left(xy-1\right)\left(x+y\right)\)
a)\(x^4-x^3-x^2+1\)
\(=x^3\left(x-1\right)-\left(x^2-1\right)\)
\(=x^3\left(x-1\right)-\left(x-1\right)\left(x+1\right)\)
\(=\left(x-1\right)\left(x^3-x-1\right)\)
d) x4 + x2 + 1
= ( x4 + 2x2 + 1) - x2
= ( x2 + 1)2 - x2
= ( x2 + 1 + x2 ).( x2 + 1 - x2 )