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