## anonymous 5 years ago Factor this polynomial completely: x4– 25.

1. anonymous

(x^2+5)(x^2-5)

2. anonymous

difference of two squares: $a^2-b^2=(a+b)(a-b)$ here $a=x^2$ $b=5$ so get $(x^2+5)(x^2-5)$

3. anonymous

$x^2+5$ does not factor, but $x^2-5$ does as $(x+\sqrt{5})(x-\sqrt{5})$