Factor. x^4-9

(x^2-3i) (x^2 + 3i)
(x-3) (x+3)
(x^2 -3) (x^2 + 3)
(x^2 - 3) (x^2 -3)

(x² - 3)(x² + 3)

Step-by-step explanation:

- 9 ← is a difference of squares and factors in general as

a² - b² = (a - b)(a + b) , thus

- 9

= (x² )² - 3²

= (x² - 3)(x² + 3)

you need to rotate this triangle about the origin 270 degrees clockwise to create the full square.