Lời giải:
a)
\(x^5+x^3-x^2-1=(x^5-x^2)+(x^3-1)\)
\(=x^2(x^3-1)+(x^3-1)=(x^2+1)(x^3-1)\)
\(=(x^2+1)(x-1)(x^2+x+1)\)
b) \(x^4-3x^3-x+3=(x^4-x)-(3x^3-3)\)
\(=x(x^3-1)-3(x^3-1)\)
\(=(x^3-1)(x-3)=(x-1)(x^2+x+1)(x-3)\)
c) \(x^3-x^2y-xy^2+y^3\)
\(=x^2(x-y)-y^2(x-y)\)
\(=(x-y)(x^2-y^2)=(x-y)(x-y)(x+y)=(x-y)^2(x+y)\)