a ) \(x^2-4+\left(x-2\right)^2\)
\(=x^2-4+x^2-4x+4\)
\(=2x^2-4x\)
\(=2x\left(x-2\right)\)
b ) \(x^3+2x^2+x+2\)
\(=x^2\left(x+2\right)+x+2\)
\(=\left(x^2+1\right)\left(x+2\right)\)
c ) \(x^3-2x^2+x-xy^2\)
\(=x\left(x^2-2x+1-y^2\right)\)
\(=x\left[\left(x-1\right)^2-y^2\right]\)
\(=x\left(x-1-y\right)\left(x-1+y\right)\)
d ) \(x^2-3x+2\)
\(=x^2-2x-x+2\)
\(=x\left(x-2\right)-\left(x-2\right)\)
\(=\left(x-1\right)\left(x-2\right)\)