Câu 34:
a) x^4+2x^3+x^2
=x^4+x^3+x^3+x^2
=x^3(x+1)+x^2(x+1)
=(x+1)(x^3+x^2)
=x^2(x+1)^2
b) x^3-x+3x^2y+3xy^2+y^3-y
=(x^3+y^3)+(3x^2y+3xy^2)-(x+y)
=(x+y)(x^2-xy+y^2)+3xy(x+y)-(x-y)
=(x+y)(x^2+y^2-xy+3xy-1)
=(x+y)((x+y)^2-1)
=(x+y)(x+y-1)(x+y+1)
c)5x^2-10xy+5y^2-20z^2
=5(x^2-2xy+y^2-4z^2)...