Đáp án:
$ x^4+6x^3-11x^2+6x+1$
$=(x^4+1)+(6x^3+6x)-11x^2$
$=(x^2+1)^2-2x^2+6x(x^2+1)-11x^2$
$=(x^2+1)^2+6x(x^2+1)-13x^2$
$=(x^2+1)^2+2(x^2+1)3x+9x^2-22x^2$
$=(x^2+1+3x)^2-(x$$\sqrt{22})^2$
$=(x^2+3x+1-x$$\sqrt{22})(x^2+3x+1+x$ $\sqrt{22})$
$=(x^2+(3-$$\sqrt{22})x+1)(x^2+(3+$ $\sqrt{22})x+1$