a, \(x^3-x^2y-xy^2+y^3\)

\(=x^2\left(x-y\right)-y^2\left(x-y\right)\)

\(=\left(x^2-y^2\right)\left(x-y\right)\)

\(=\left(x-y\right)^2\left(x+y\right)\)

b, \(x^3+x^2-4x-4\)

\(=x^2\left(x+1\right)-4\left(x+1\right)\)

\(=\left(x^2-4\right)\left(x+1\right)=\left(x-2\right)\left(x+2\right)\left(x+1\right)\)

c, \(x^3-x^2-x+1\)

\(=x^2\left(x-1\right)-\left(x-1\right)=\left(x^2-1\right)\left(x-1\right)\)

\(=\left(x-1\right)^2\left(x+1\right)\)

d, \(\left(7x+3\right)^2-\left(2x-1\right)^2\)

\(=\left(7x+3-2x+1\right)\left(7x+3+2x-1\right)\)

\(=\left(5x+4\right)\left(9x+2\right)\)

e, \(x^3-3x^2-3x+1\) sai đề

f, \(x^2-2x-3\)

\(=x^2-3x+x-3=x\left(x-3\right)+\left(x-3\right)\)

\(=\left(x+1\right)\left(x-3\right)\)

g, \(x^2-2x-8\)

\(=x^2-4x+2x-8=x\left(x-4\right)+2\left(x-8\right)\)

\(=\left(x+2\right)\left(x-8\right)\)

h, \(x^2-10x+21\)

\(=x^2-7x-3x+21\)

\(=x\left(x-7\right)-3\left(x-7\right)=\left(x-3\right)\left(x-7\right)\)

i, \(x^2-4xy+3y^2\)

\(=x^2-4xy+4y^2-y^2\)

\(=\left(x-2y\right)^2-y^2\)

\(=\left(x-2y-y\right)\left(x-2y+y\right)\)

\(=\left(x-3y\right)\left(x-y\right)\)