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